Free developer tools for the small jobs between coding and shipping.
Format JSON and SQL, test regex, decode tokens, inspect URLs, compare code, and generate test data directly in your browser.
- Browser-local processing
- No account required
- Copy-ready output
Choose by debugging task
Start with what you are debugging
The time sink is usually reading a value by eye: a minified response, a token you are guessing the contents of, or a pattern that almost matches. These paths make the value readable first, then check it before it reaches a commit.
- 01
Read & compare data
Make a payload readable, validate its structure, or inspect what changed between two versions.
Start hereJSON Formatter - 02
Recover broken payloads
Repair malformed or AI-generated JSON with the line, the rule and the evidence behind every correction.
Start hereJSON Repair Pro - 03
Inspect encoded values
Break down tokens and URLs, or move safely between readable and encoded text.
Start hereJWT Decoder - 04
Create test inputs
Generate identifiers, typed interfaces, schedules, and realistic sample records.
Start hereUUID/GUID Generator - 05
Validate before shipping
Test patterns, check contrast, and clean output without adding another package to the project.
Start hereRegex Tester
Have a payload but no clear starting point? Open JSON Formatter to validate it and expose the structure before you convert or compare anything.
Tool directory
Developer tools
Showing 19 of 19 tools
JSON Formatter
Format, validate, repair, explore, query, compare and convert JSON in one browser workspace — with precise error locations, a tree editor, schema tools and type generation for eight languages.
CSV to JSON Converter
Convert, clean, map and validate CSV and JSON in one browser workspace — with delimiter and encoding detection, column profiling, header repair, nested output, row-level validation and eight export formats.
UUID/GUID Generator
Generate 1 to 5,000 random version 4 UUIDs with optional hyphens, uppercase letters, braces, and quotes.
JWT Decoder
Decode JWT header, payload, signature, registered claims, and expiry, with optional client-side HMAC verification for HS256, HS384, and HS512.
Regex Tester
Test JavaScript regular expressions against sample text with live match highlighting, capture groups, match counts, and flag controls.
JSON to TypeScript
Generate TypeScript interfaces from valid JSON objects and nested API-response samples, with copying and `.ts` download.
SQL Formatter
Format SQL with uppercase keywords and two-space indentation for six selectable database dialects.
Cron Expression Generator
Build a five-field cron expression, read its plain-English interpretation, inspect field guidance, and copy the result.
Base64 Encoder / Decoder
Encode Unicode text as Base64 or decode Base64 back to readable UTF-8 text, with copying, swapping, samples, and text download.
URL Encoder / Decoder
Percent-encode URL components or decode percent-encoded text, with samples, swapping, copying, and text download.
JSON Repair Pro
Repair malformed and AI-generated JSON with line-level explanations, reviewable changes and local processing.
Color Contrast Checker
Check WCAG 2.2 contrast for text, UI components, icons, and meaningful graphics, then preview and apply nearby passing color alternatives.
URL Query Parser
Parse a URL into its base path, hash fragment, and editable query parameters, then rebuild and copy the result.
Mock Data Generator
Generate up to 1,000 synthetic profile records as JSON or CSV with selectable fields for development and UI testing.
Hash Generator
Generate MD5, SHA-1, SHA-256, and SHA-512 hexadecimal digests from text as you type, with individual copy controls.
HTML Formatter
Beautify HTML with two-space indentation or minify spacing, with byte statistics, copying, samples, and file download.
CSS Minifier
Remove CSS comments and unnecessary whitespace, show size savings, and copy or download the minified stylesheet.
JS Beautifier
Expand minified or cramped JavaScript into readable two-space-indented code with copying, samples, and `.js` download.
Code Compare
Compare two text or code versions in a Monaco diff editor with split or inline views, syntax modes, file loading, statistics, and fullscreen.
Practical category guide
A practical workflow for one-off developer tasks
Developer utilities are most useful when they remove a small interruption without becoming another setup task. Use this collection to inspect an unfamiliar API response, compare two configuration files, test a regular expression against representative input, decode a token while tracing authentication, format a query for review, or create realistic fixtures for a test. The tools are deliberately single-purpose: the input, transformation, and result remain visible, so you can verify the output before copying it back into an editor, terminal, issue, or pull request.
What these Developer tools help with
Inspect without a round trip
Open an API response in the JSON Formatter or compare two revisions in Code Compare without creating a scratch script or switching to a heavyweight workspace.
See exactly what changed
Formatters separate syntax from content, while Code Compare and the Regex Tester make differences and matches visible before you copy a result downstream.
Build realistic test inputs
Use the Mock Data Generator for representative records, the UUID/GUID Generator for identifiers, and JSON to TypeScript when a sample payload needs a typed interface.
Keep the operation understandable
Each tool handles one explicit transformation and keeps its controls in view, which makes the result easier to review than a hidden multi-step conversion.
Selection guide
Four developer-tool workflows
Start with the smallest tool that answers the question, then add a second step only when the result needs validation or conversion.
- 1
Understand an API response
Run the payload through JSON Formatter first. Continue with JSON to TypeScript when you need an interface, or Code Compare when the question is what changed between responses.
- 2
Trace an authentication or URL issue
Use JWT Decoder to inspect claims without treating them as verified, URL Query Parser to isolate parameters, and Base64 Encoder / Decoder only when the value is actually Base64-encoded.
- 3
Prepare fixtures and schedules
Create representative records with Mock Data Generator, add identifiers with UUID/GUID Generator, and use Cron Expression Generator to make a schedule readable before it reaches a job runner.
- 4
Validate before you commit
Exercise a pattern in Regex Tester, check text and background colors with Color Contrast Checker, then use a formatter or CSS Minifier only after the readable source is reviewed.
Practical ways to use Developer tools
- 01
Pretty-print a minified API response in JSON Formatter, then compare it with a previous response in Code Compare.
- 02
Inspect a short-lived test token's claims and expiry in JWT Decoder while tracing an authentication failure.
- 03
Test a regular expression against positive, negative, and edge-case samples in Regex Tester before adding it to an application.
- 04
Turn a representative JSON payload into a starting interface with JSON to TypeScript, then review optional fields and unions by hand.
- 05
Create mock records and UUIDs for fixtures without copying personal data from a production database.
- 06
Parse a long callback URL with URL Query Parser to inspect redirect, state, and tracking parameters independently.
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