Screen capture, diagramming, note taking, editing, and general utilities frequently used by testers.
D
D3.js
Use case: Build data-driven charts and visualizations for test results or analysis.
Type: Open-source JavaScript visualization library
Access: Free and open source
Also known as: d3
What It Does
According to the vendor or project, the tool's stated purpose is to build data-driven charts and visualizations for test results or analysis.
Positive Community Commentary
Technically inclined testers value D3.js when standard charts cannot explain a complicated quality signal or test dataset. Its direct control over SVG, scales, interactions, and data binding makes it possible to build tailored defect, coverage, timing, and relationship visualizations that expose patterns hidden in tables, while remaining part of a normal web application.
Things to Know
- Product or project type: Open-source JavaScript visualization library.
- Current access model: Free and open source.
- Review the official page for current platforms, integrations, system requirements, licensing, and product changes.
Visit the D3.js website
Information checked: August 5, 2026
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DevToys
Use case: Use encoders, decoders, formatters, generators, and converters in one desktop application.
Type: Open-source developer utility suite
Access: Free and open source
What It Does
According to the vendor or project, the tool's stated purpose is to use encoders, decoders, formatters, generators, and converters in one desktop application.
Positive Community Commentary
Developers and testers praise DevToys as a convenient offline toolbox for everyday transformations such as JSON formatting, Base64 and URL encoding, hashing, UUID generation, text comparison, and regular-expression work. Keeping these small utilities in one desktop application reduces browser searching and is particularly valued when sample data or logs should remain local.
Things to Know
- Product or project type: Open-source developer utility suite.
- Current access model: Free and open source.
- Review the official page for current platforms, integrations, system requirements, licensing, and product changes.
Visit the DevToys website
Information checked: August 5, 2026
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Dia Diagram Editor
Use case: Create flowcharts, network diagrams, and other technical diagrams.
Type: Open-source diagramming application
Access: Free and open source
What It Does
According to the vendor or project, the tool's stated purpose is to create flowcharts, network diagrams, and other technical diagrams.
Positive Community Commentary
Open-source users value Dia as a lightweight way to create flowcharts, network maps, state diagrams, and other technical sketches without a subscription or complex collaboration platform. Its large shape library, straightforward connectors, and export options make it useful for documenting test environments and system flows that need a clear, portable diagram rather than a polished workshop board.
Things to Know
- Product or project type: Open-source diagramming application.
- Current access model: Free and open source.
- Review the official page for current platforms, integrations, system requirements, licensing, and product changes.
Visit the Dia Diagram Editor website
Information checked: August 5, 2026
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draw.io
Use case: Create flowcharts, architecture diagrams, mind maps, and process diagrams.
Type: Diagramming application
Access: Free web and desktop editions
What It Does
According to the vendor or project, the tool's stated purpose is to create flowcharts, architecture diagrams, mind maps, and process diagrams.
Positive Community Commentary
Testers and architects frequently praise draw.io for its broad shape library, quick connectors, templates, and ability to save diagrams locally or through common cloud repositories. It is widely used for system context, data flow, test architecture, and process diagrams because collaborators can open the files easily and the tool works without requiring a specialized modeling background.
Things to Know
- Product or project type: Diagramming application.
- Current access model: Free web and desktop editions.
- Review the official page for current platforms, integrations, system requirements, licensing, and product changes.
Visit the draw.io website
Information checked: August 5, 2026
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J
JSON Compare
Use case: Compare two JSON documents and highlight semantic differences.
Type: Online JSON comparison tool
Access: Free web tool
What It Does
According to the vendor or project, the tool's stated purpose is to compare two JSON documents and highlight semantic differences.
Positive Community Commentary
API testers and developers can use JSON Compare when expected and actual payloads need more than a plain text diff. By formatting and comparing object keys, values, arrays, and structures, it helps reviewers spot missing fields, changed values, and response-shape differences that matter when validating API responses, configuration files, fixtures, or generated data.
Things to Know
- Product or project type: Online JSON comparison tool.
- Current access model: Free web tool.
- Review the official page for current platforms, integrations, system requirements, licensing, and product changes.
Visit the JSON Compare website
Information checked: August 24, 2026
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JSON Compare (JSONViewerTool)
Use case: Compare two JSON documents side by side and review a semantic summary of changes.
Type: Online JSON comparison tool
Access: Free web tool without an account
What It Does
According to the vendor, JSON Compare highlights changed values, added or missing keys, and array differences in two JSON documents. It offers a side-by-side diff and a JSON Patch-style semantic summary.
Positive Community Commentary
API testers can use it to inspect changes between expected and actual responses, environment snapshots, or regression fixtures. The visual view provides context around each difference, while the semantic summary can make field-level changes easier to describe in a bug report or review.
Things to Know
- Product or project type: Online JSON comparison tool from JSONViewerTool.
- Current access model: Free web tool without an account.
- The tool offers controls for ignoring object key order or array order. Because array order can matter in API responses, use that option only when order is irrelevant to the test.
- The site offers JSON Patch-style and unified diff exports. Review exported changes before using them in an automated workflow.
- The vendor states that comparison runs in the browser and that JSON payloads are not uploaded; AT*SQA has not independently verified this claim.
Visit the JSON Compare website at JSONViewerTool
Information checked: October 12, 2026
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JSON Crack
Use case: Visualize, edit, and inspect JSON and related data formats.
Type: JSON visualization and editing tool
Access: Free web tool with paid options
What It Does
According to the vendor or project, the tool's stated purpose is to visualize, edit, and inspect JSON and related data formats.
Positive Community Commentary
Developers and testers value JSON Crack for turning deeply nested JSON, YAML, XML, CSV, and related structures into an explorable visual graph. It is particularly useful when tracing object relationships, spotting unexpected nesting, explaining an API payload to teammates, or navigating test data that is difficult to understand in a conventional text viewer.
Things to Know
- Product or project type: JSON visualization and editing tool.
- Current access model: Free web tool with paid options.
- Review the official page for current platforms, integrations, system requirements, licensing, and product changes.
Visit the JSON Crack website
Information checked: August 5, 2026
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JSON Fixer
Use case: Use AI assistance to repair malformed JSON or adjust JSON data.
Type: AI-assisted JSON repair tool
Access: Free web tool
What It Does
According to the vendor or project, the tool's stated purpose is to use AI assistance to repair malformed JSON or adjust JSON data.
Positive Community Commentary
Testers can use JSON Fixer as a quick aid when copied payloads, logs, or examples contain missing commas, quote issues, invalid values, or other problems that prevent normal parsing. It is most useful as a starting point for repairing sample data, with the corrected output reviewed carefully before it is used in a test, defect report, or automated workflow.
Things to Know
- Product or project type: AI-assisted JSON repair tool.
- Current access model: Free web tool.
- Review the official page for current platforms, integrations, system requirements, licensing, and product changes.
Visit the JSON Fixer website
Information checked: August 24, 2026
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JSON Formatter
Use case: Beautify, minify, escape, unescape, and visualize JSON.
Type: Online JSON formatter and viewer
Access: Free web tool
What It Does
According to the vendor or project, the tool's stated purpose is to beautify, minify, escape, unescape, and visualize JSON.
Positive Community Commentary
Testers and developers use JSON formatters constantly when raw API responses, configuration snippets, or generated payloads are too compact to review comfortably. JSON Formatter is useful for turning minified data into readable indentation, preparing compact examples, escaping or unescaping JSON strings, and opening a tree view when a nested response needs to be inspected quickly.
Things to Know
- Product or project type: Online JSON formatter and viewer.
- Current access model: Free web tool.
- Review the official page for current platforms, integrations, system requirements, licensing, and product changes.
Visit the JSON Formatter website
Information checked: August 24, 2026
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JSON Generator
Use case: Generate JSON test data from templates and helper functions.
Type: Online JSON test-data generator
Access: Free web tool
What It Does
According to the vendor or project, the tool's stated purpose is to generate JSON test data from templates and helper functions.
Positive Community Commentary
Testers can use JSON Generator to create structured sample payloads without hand-writing every field. Template helpers for random values, booleans, dates, choices, repeated arrays, indexes, names, countries, cities, and expressions make it useful for producing lightweight API fixtures, demo datasets, exploratory test inputs, or multiple JSON files with similar structure.
Things to Know
- Product or project type: Online JSON test-data generator.
- Current access model: Free web tool.
- Review the official page for current platforms, integrations, system requirements, licensing, and product changes.
Visit the JSON Generator website
Information checked: August 24, 2026
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JSON Merger
Use case: Merge two JSON documents into a combined JSON result.
Type: Online JSON merge tool
Access: Free web tool
What It Does
According to the vendor or project, the tool's stated purpose is to merge two JSON documents into a combined JSON result.
Positive Community Commentary
Testers can use JSON Merger when separate configuration fragments, mock data files, or copied API examples need to be combined for a quick experiment. It is especially handy when building temporary fixtures or checking how overlapping object structures will resolve before the result is placed into a test environment, script, or shared defect example.
Things to Know
- Product or project type: Online JSON merge tool.
- Current access model: Free web tool.
- Review the official page for current platforms, integrations, system requirements, licensing, and product changes.
Visit the JSON Merger website
Information checked: August 24, 2026
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JSON Patch Generator
Use case: Generate RFC 6902 JSON Patch operations from source and target JSON.
Type: Online JSON Patch generator
Access: Free web tool
What It Does
According to the vendor or project, the tool's stated purpose is to generate RFC 6902 JSON Patch operations from source and target JSON.
Positive Community Commentary
API testers and integrators can use JSON Patch Generator to understand or create the add, remove, replace, and related operations needed to move one JSON document to another. It is useful when validating PATCH endpoints, documenting expected partial updates, building examples for contract discussions, or comparing how a client should express a change without resending the full object.
Things to Know
- Product or project type: Online JSON Patch generator.
- Current access model: Free web tool.
- Review the official page for current platforms, integrations, system requirements, licensing, and product changes.
Visit the JSON Patch Generator website
Information checked: August 24, 2026
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JSON Samples
Use case: Copy or download sample JSON objects and arrays for learning, testing, and templates.
Type: JSON example collection
Access: Free web resource
What It Does
According to the vendor or project, the tool's stated purpose is to provide sample JSON objects and arrays for learning, testing, and templates.
Positive Community Commentary
Testers can use JSON Samples when they need realistic-looking structures to practice parsing, explain JSON basics, seed a quick demo, or build a starting fixture. Ready-to-copy object, array, profile, product, and configuration examples are useful when the exact content is less important than having a valid nested structure to exercise a tool or workflow.
Things to Know
- Product or project type: JSON example collection.
- Current access model: Free web resource.
- Review the official page for current platforms, integrations, system requirements, licensing, and product changes.
Visit the JSON Samples website
Information checked: August 24, 2026
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JSON to JSON Schema
Use case: Generate a starter JSON Schema from JSON input.
Type: Online JSON Schema generator
Access: Free web tool
What It Does
According to the vendor or project, the tool's stated purpose is to generate a starter JSON Schema from JSON input.
Positive Community Commentary
API testers can use JSON to JSON Schema to quickly turn an example response or request body into a draft schema for validation, documentation, or contract conversations. The generated schema is best treated as a starting point that still needs human review, especially for required fields, optional values, formats, and constraints that cannot be inferred reliably from one sample.
Things to Know
- Product or project type: Online JSON Schema generator.
- Current access model: Free web tool.
- Review the official page for current platforms, integrations, system requirements, licensing, and product changes.
Visit the JSON to JSON Schema website
Information checked: August 24, 2026
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JSON to JSONL
Use case: Convert JSON arrays or objects into JSON Lines format.
Type: Online JSON-to-JSONL converter
Access: Free web tool
What It Does
According to the vendor or project, the tool's stated purpose is to convert JSON arrays or objects into JSON Lines format.
Positive Community Commentary
Testers working with logs, large datasets, or data-processing pipelines can use JSON to JSONL when a conventional JSON array needs to become one JSON record per line. That format is easier to stream, split, append, and process sequentially, which makes it useful for performance investigations, analytics checks, machine-learning datasets, and command-line data workflows.
Things to Know
- Product or project type: Online JSON-to-JSONL converter.
- Current access model: Free web tool.
- Review the official page for current platforms, integrations, system requirements, licensing, and product changes.
Visit the JSON to JSONL website
Information checked: August 24, 2026
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JSON to Protobuf
Use case: Generate a Protocol Buffers schema and binary data from JSON input.
Type: Online JSON-to-Protobuf converter
Access: Free web tool
What It Does
According to the vendor or project, the tool's stated purpose is to generate a Protocol Buffers schema and binary data from JSON input.
Positive Community Commentary
Testers and developers can use JSON to Protobuf when they need to explore how a JSON sample might map to a .proto schema or binary Protocol Buffers data. It can help with early API discussions, serialization experiments, and fixture preparation for systems that use compact binary messages, while still requiring review before the generated schema is treated as authoritative.
Things to Know
- Product or project type: Online JSON-to-Protobuf converter.
- Current access model: Free web tool.
- Review the official page for current platforms, integrations, system requirements, licensing, and product changes.
Visit the JSON to Protobuf website
Information checked: August 24, 2026
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JSON to TOON
Use case: Convert JSON into TOON format for compact LLM-oriented prompts.
Type: Online JSON-to-TOON converter
Access: Free web tool
What It Does
According to the vendor or project, the tool's stated purpose is to convert JSON into TOON format for compact LLM-oriented prompts.
Positive Community Commentary
Testers experimenting with AI-assisted workflows can use JSON to TOON when structured payloads or fixture data need to be provided to a language model in a compact, readable representation. It is most relevant for uniform arrays of objects and prompt examples where token efficiency matters, while JSON remains the safer default for programmatic interchange and deeply nested or irregular data.
Things to Know
- Product or project type: Online JSON-to-TOON converter.
- Current access model: Free web tool.
- Review the official page for current platforms, integrations, system requirements, licensing, and product changes.
Visit the JSON to TOON website
Information checked: August 24, 2026
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JSON Validator
Use case: Check JSON syntax and highlight errors.
Type: Online JSON syntax validator
Access: Free web tool
What It Does
According to the vendor or project, the tool's stated purpose is to check JSON syntax and highlight errors.
Positive Community Commentary
Testers can use JSON Validator when copied responses, fixture files, configuration snippets, or hand-edited payloads fail to parse and the error location is not obvious. Immediate syntax checking helps find missing commas, unquoted keys, bracket mismatches, unsupported values, and similar defects before invalid data is blamed on an API, test runner, or application under test.
Things to Know
- Product or project type: Online JSON syntax validator.
- Current access model: Free web tool.
- Review the official page for current platforms, integrations, system requirements, licensing, and product changes.
Visit the JSON Validator website
Information checked: August 24, 2026
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JSON Viewer
Use case: Format and inspect JSON documents in the browser.
Type: Browser JSON-viewing extension
Access: Free
What It Does
According to the vendor or project, the tool's stated purpose is to format and inspect JSON documents in the browser.
Positive Community Commentary
Browser users value JSON Viewer for automatically formatting raw JSON into an indented, collapsible, syntax-highlighted tree. Testers find it useful during exploratory API and web work because large responses become searchable and navigable immediately in the browser, reducing the need to copy each payload into a separate formatter.
Things to Know
- Product or project type: Browser JSON-viewing extension.
- Current access model: Free.
- Review the official page for current platforms, integrations, system requirements, licensing, and product changes.
Visit the JSON Viewer website
Information checked: August 5, 2026
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JSONL Validator
Use case: Validate JSON Lines files and highlight line-level errors.
Type: Online JSONL validation and formatting tool
Access: Free web tool
What It Does
According to the vendor or project, the tool's stated purpose is to validate JSON Lines files and highlight line-level errors.
Positive Community Commentary
Data and API testers can use JSONL Validator when each line of a file should be an independent JSON record. Line-level highlighting is useful for large logs, export files, machine-learning datasets, and streaming fixtures because one bad record can be found without treating the whole dataset as a single JSON document.
Things to Know
- Product or project type: Online JSONL validation and formatting tool.
- Current access model: Free web tool.
- Review the official page for current platforms, integrations, system requirements, licensing, and product changes.
Visit the JSONL Validator website
Information checked: August 24, 2026
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JSONPath Tester
Use case: Test JSONPath expressions against a JSON document and view the matches.
Type: Online JSONPath testing tool
Access: Free web tool
What It Does
According to the vendor or project, the tool's stated purpose is to test JSONPath expressions against a JSON document and view the matches.
Positive Community Commentary
Testers can use JSONPath Tester when an assertion, data extraction rule, monitor, or transformation depends on selecting the right fields from a nested JSON payload. Seeing the matches update against sample input helps debug path syntax, array indexing, filters, and deep searches before the expression is placed into an automated test or data-processing step.
Things to Know
- Product or project type: Online JSONPath testing tool.
- Current access model: Free web tool.
- Review the official page for current platforms, integrations, system requirements, licensing, and product changes.
Visit the JSONPath Tester website
Information checked: August 24, 2026
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M
Mermaid
Use case: Create diagrams from text-based definitions.
Type: Open-source diagramming syntax and renderer
Access: Free and open source
What It Does
According to the vendor or project, the tool's stated purpose is to create diagrams from text-based definitions.
Positive Community Commentary
Developers and testers praise Mermaid because flowcharts, sequence diagrams, state diagrams, timelines, and other visuals can live as readable text beside code and documentation. Git diffs, Markdown support, and automatic rendering make diagrams easier to update during reviews, which is valuable for test flows and architecture that change with the product.
Things to Know
- Product or project type: Open-source diagramming syntax and renderer.
- Current access model: Free and open source.
- Review the official page for current platforms, integrations, system requirements, licensing, and product changes.
Visit the Mermaid website
Information checked: August 5, 2026
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Mermaid Live Editor
Use case: Create and share test-flow and system-interaction diagrams from Mermaid text.
Type: Independently hosted Mermaid diagram editor
Access: Free web tool
What It Does
According to the site, Mermaid Live Editor lets users write or paste Mermaid text, see a live diagram preview, start from templates and examples, share diagram links, and export PNG, SVG, PDF, or MMD files.
Positive Community Commentary
Testers can use the editor to map test paths, state changes, and interactions between services, then share a diagram for review or keep its Mermaid source with project documentation. The text-based format makes these diagrams straightforward to revise as behavior and test coverage change.
Things to Know
- Product or project type: Independently hosted Mermaid diagram editor based on the upstream Mermaid Live Editor; this site is maintained separately from the Mermaid project.
- Current access model: Free web tool.
- The site says normal editing and export happen in the browser. Share links contain encoded diagram content, which anyone with the complete link can read.
- The site does not publish a public support email or issue tracker for this deployment.
Visit the Mermaid Live Editor website
Information checked: October 9, 2026
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Mindomo
Use case: Create mind maps, concept maps, and structured plans.
Type: Commercial mind-mapping platform
Access: Free and paid plans
What It Does
According to the vendor or project, the tool's stated purpose is to create mind maps, concept maps, and structured plans.
Positive Community Commentary
Users value Mindomo for combining mind maps, outlines, task information, links, notes, and collaboration in one structured view. Testers use that flexibility to brainstorm risks, organize exploratory coverage, decompose requirements, and present relationships among features and test ideas without forcing the information into a linear document too early.
Things to Know
- Product or project type: Commercial mind-mapping platform.
- Current access model: Free and paid plans.
- Review the official page for current platforms, integrations, system requirements, licensing, and product changes.
Visit the Mindomo website
Information checked: August 5, 2026
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Miro
Use case: Collaborate on diagrams, workshops, test planning, and retrospectives.
Type: Commercial collaborative whiteboard
Access: Free and paid plans
What It Does
According to the vendor or project, the tool's stated purpose is to collaborate on diagrams, workshops, test planning, and retrospectives.
Positive Community Commentary
Testing teams value Miro for collaborative risk workshops, example mapping, story reviews, retrospectives, and visual test planning with remote participants. Its infinite canvas, sticky notes, voting, timers, templates, and integrations let a group externalize ideas quickly, cluster them, and turn the workshop output into an agreed set of risks or actions.
Things to Know
- Product or project type: Commercial collaborative whiteboard.
- Current access model: Free and paid plans.
- Review the official page for current platforms, integrations, system requirements, licensing, and product changes.
Visit the Miro website
Information checked: August 5, 2026
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Mock API
Use case: Create temporary mock REST APIs from JSON resources and custom response rules.
Type: Open-source mock API and web service
Access: Free web tool with open-source local option
What It Does
According to the vendor or project, the tool's stated purpose is to create temporary mock REST APIs from JSON resources and custom response rules.
Positive Community Commentary
API testers and developers can use Mock API to stand up quick resources for prototyping, exploratory testing, demos, or client-side work before a real service is ready. JSON-defined resources, common REST routes, custom rules, response headers, status codes, and a local open-source option make it useful for exercising success and error cases without building a full backend.
Things to Know
- Product or project type: Open-source mock API and web service.
- Current access model: Free web tool with open-source local option.
- Review the official page for current platforms, integrations, system requirements, licensing, and product changes.
Visit the Mock API website
Information checked: August 24, 2026
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Monosnap
Use case: Capture, annotate, record, and share visual evidence.
Type: Commercial screenshot and screen-recording tool
Access: Free and paid plans
What It Does
According to the vendor or project, the tool's stated purpose is to capture, annotate, record, and share visual evidence.
Positive Community Commentary
Users value Monosnap for combining screenshots, annotation, short recordings, blur tools, and quick sharing in a single lightweight workflow. Testers find it useful when a defect needs both a clearly marked still image and a short reproduction clip, with upload and link options that make the evidence easy to place in an issue.
Things to Know
- Product or project type: Commercial screenshot and screen-recording tool.
- Current access model: Free and paid plans.
- Review the official page for current platforms, integrations, system requirements, licensing, and product changes.
Visit the Monosnap website
Information checked: August 5, 2026
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