18 Free Developer Tools You Can Use Right Now

Every developer has a handful of go-to utilities bookmarked across half a dozen different websites. A JSON formatter here, a Base64 converter there, a UUID generator somewhere else. We built BlestLabs Dev Toolkit to put all of these into one place — 18 tools, completely free, running entirely in your browser so your data never touches a server.

Here is every tool in the toolkit and why you might reach for it.

JSON Tools

1. JSON Formatter

Paste messy, minified, or malformed JSON and get clean, indented output instantly. The formatter validates your JSON as you type, highlights syntax errors with line numbers, and lets you toggle between 2-space and 4-space indentation. You can also minify JSON to reduce payload size before shipping it to an API.

Use case: Debugging API responses, cleaning up config files, validating webhook payloads.

Try the JSON Formatter

2. JSON to TypeScript

Feed in a JSON object and get back a fully typed TypeScript interface or type alias. The converter handles nested objects, arrays of mixed types, optional fields, and even generates union types when it detects varying array element shapes.

Use case: Quickly scaffolding types for a new API integration instead of writing interfaces by hand.

Try JSON to TypeScript

Encoding Tools

3. Base64 Encode/Decode

Convert any text to Base64 and back with full UTF-8 support. Handles international characters, emoji, and multi-byte sequences without corruption.

Use case: Encoding credentials for HTTP headers, decoding data URIs, inspecting email attachments.

Try Base64 Encoder

4. URL Encode/Decode

Encode special characters in URLs so they survive transit through query strings, path segments, and form submissions. Decode percent-encoded strings back to readable text.

Use case: Debugging query parameters, constructing OAuth redirect URIs, fixing broken links with special characters.

Try URL Encoder

5. HTML Entity Encoder/Decoder

Convert characters like <, >, &, and " into their HTML entity equivalents (<, >, &, ") and back. Supports both named and numeric entities.

Use case: Sanitizing user input for safe HTML rendering, decoding scraped HTML content, fixing garbled text in email templates.

Try HTML Entity Encoder

6. Number Base Converter

Convert numbers between binary, octal, decimal, and hexadecimal. Supports large numbers and shows a bitwise visualization so you can see exactly which bits are set.

Use case: Working with bitwise flags, reading memory addresses, converting color values between hex and decimal.

Try Number Base Converter

Generator Tools

7. UUID Generator

Generate cryptographically random UUID v4 identifiers one at a time or in bulk — up to 100 at once. Each UUID is copy-ready with a single click.

Use case: Creating database primary keys, generating unique session tokens, seeding test data.

Try UUID Generator

8. Lorem Ipsum Generator

Generate placeholder text by word count, sentence count, or paragraph count. The output is clean, copy-ready Latin text for mockups, wireframes, and prototypes.

Use case: Filling design mockups, testing text overflow, populating CMS templates during development.

Try Lorem Ipsum Generator

9. Cron Expression Parser

Enter a cron expression and see a human-readable description of the schedule, the next five execution times, and a field-by-field breakdown. Includes common presets for quick reference.

Use case: Verifying CI/CD pipeline schedules, debugging scheduled tasks, documenting cron jobs for your team.

Try Cron Parser

10. Unix Timestamp Converter

Convert between Unix timestamps (seconds or milliseconds) and human-readable dates in multiple formats. Shows the current timestamp, ISO 8601, and relative time ("3 hours ago").

Use case: Debugging log timestamps, converting API date fields, checking JWT expiration times.

Try Timestamp Converter

Text Tools

11. Regex Tester

Write a regular expression, paste your test string, and see all matches highlighted in real time. Supports global, case-insensitive, multiline, and dotAll flags. Shows capture groups and match indices.

Use case: Building validation patterns, extracting data from logs, testing find-and-replace operations before running them in code.

Try Regex Tester

12. Text Diff Checker

Paste two text blocks side by side and see additions, deletions, and changes highlighted at the character level. Useful for comparing config files, code snippets, or any two blocks of text.

Use case: Reviewing config changes, comparing API response versions, auditing content edits.

Try Diff Checker

13. String Case Converter

Convert text between camelCase, PascalCase, snake_case, kebab-case, SCREAMING_SNAKE_CASE, Title Case, and more. Click any result to copy it.

Use case: Renaming variables across conventions, converting database column names to code-friendly formats, formatting API field names.

Try Case Converter

14. Markdown Preview

A split-pane Markdown editor with live preview. Supports GitHub Flavored Markdown — tables, task lists, fenced code blocks, strikethrough, and autolinks.

Use case: Writing README files, drafting documentation, previewing PR descriptions before submitting.

Try Markdown Preview

Web Tools

15. JWT Decoder

Paste a JSON Web Token and instantly see the decoded header, payload, and signature. The decoder checks expiration (exp), issued-at (iat), and not-before (nbf) claims and warns you if the token is expired.

Use case: Debugging authentication issues, inspecting token claims, verifying token structure before deployment.

Try JWT Decoder

16. Color Converter

Enter a color in HEX, RGB, or HSL format and see instant conversions to all three formats with a live preview swatch. Useful for translating design specs into CSS values.

Use case: Converting Figma hex values to RGB for CSS, adjusting HSL lightness for hover states, matching brand colors across formats.

Try Color Converter

17. CSS Minifier/Beautifier

Paste CSS to minify it (strip whitespace, comments, and redundancy) or beautify minified CSS back to readable form. Shows character count and compression savings.

Use case: Optimizing stylesheets for production, making minified vendor CSS readable for debugging, comparing file sizes.

Try CSS Minifier

Crypto Tools

18. Hash Generator

Generate MD5, SHA-1, SHA-256, and SHA-512 hashes from any text input. Uses the browser's native Web Crypto API for fast, secure computation — nothing is sent to a server.

Use case: Verifying file integrity, generating content hashes for caching, creating checksums for data validation.

Try Hash Generator

Why Client-Side Matters

Every tool in the BlestLabs Dev Toolkit runs entirely in your browser. Your JSON, your tokens, your passwords — none of it leaves your machine. There is no backend processing, no logging, no analytics on your input data. This is not just a privacy feature; it is the architecture. The tools work offline, load instantly, and will never leak your data because there is no server to leak it to.

Getting Started

Head to the Dev Toolkit to browse all 18 tools. Each tool has its own page with a dedicated URL you can bookmark, and the sidebar lets you jump between tools without losing your place. No sign-up required — just open and use.