73 Free Online Tools Every Developer Should Bookmark in 2026

Your Browser Is a Development Toolkit

Every developer has a collection of tools they reach for daily. Formatters, encoders, decoders, converters, testers, generators — the list grows with every project. The best of these tools run entirely in the browser, require no signup, and do exactly one thing well.

This is a curated list of 73 free online tools organized by category. Whether you are a frontend developer, backend engineer, DevOps specialist, or full-stack generalist, you will find something here you did not know you needed.

Code Formatting and Beautification

Readable code is maintainable code. These tools take minified or poorly formatted code and make it human-readable.

1. JSON Formatter — Parse, validate, and pretty-print JSON with syntax highlighting. The JSON Formatter on UtilityDocker handles large payloads instantly in your browser.
2. SQL Formatter — Indent and format SQL queries for readability. The SQL Formatter supports multiple SQL dialects and customizable indentation.
3. HTML Formatter — Beautify messy HTML with proper indentation and tag alignment.
4. CSS Formatter — Expand minified CSS into readable, organized stylesheets.
5. JavaScript Beautifier — Restore minified JS to readable source with proper formatting.
6. XML Formatter — Indent and validate XML documents.
7. YAML Formatter — Validate and format YAML configuration files.
8. Markdown Preview — Write Markdown and see the rendered HTML output in real time.

Code Minification

The opposite of formatting — reduce code size for production deployment.

9. Code Minifier — Minify JavaScript, CSS, and HTML in one tool. The Code Minifier strips whitespace, comments, and unnecessary characters to reduce file size.
10. CSS Minifier — Remove whitespace, comments, and redundant rules from CSS files.
11. JavaScript Minifier — Compress JS by removing whitespace and shortening variable names.
12. SVG Optimizer — Remove unnecessary metadata and simplify SVG paths.

Testing and Validation

Catch bugs before they reach production.

13. Regex Tester — Write, test, and debug regular expressions with real-time matching and group capture display. The Regex Tester is indispensable for pattern matching work.
14. JSON Validator — Verify that JSON is syntactically correct and identify the exact location of errors.
15. HTML Validator — Check HTML documents against W3C standards.
16. CSS Validator — Find errors and warnings in CSS stylesheets.
17. JWT Decoder — Decode JSON Web Tokens to inspect the header, payload, and signature. The JWT Decoder is essential for debugging authentication flows.
18. Cron Expression Tester — Write cron expressions and see the next scheduled execution times.
19. API Request Builder — Construct and send HTTP requests directly from the browser.
20. Schema Validator — Validate JSON data against JSON Schema definitions.

Encoding and Decoding

Convert data between formats safely.

21. Base64 Encoder/Decoder — Encode binary data to Base64 or decode Base64 strings.
22. URL Encoder/Decoder — Percent-encode strings for safe use in URLs or decode encoded URLs.
23. HTML Entity Encoder — Convert special characters to HTML entities and vice versa.
24. JWT Encoder — Create JWTs with custom headers, payloads, and signing algorithms.
25. Unicode Lookup — Search for Unicode characters by name, code point, or appearance.
26. Hex to ASCII Converter — Convert hexadecimal strings to readable ASCII text.
27. Binary to Decimal Converter — Convert between binary, decimal, hexadecimal, and octal.

Generators

Create boilerplate, test data, and identifiers.

28. UUID Generator — Generate UUIDs (v1, v4, v7) for use as unique identifiers.
29. Lorem Ipsum Generator — Generate placeholder text for design mockups.
30. Password Generator — Create strong, random passwords with configurable length and character sets.
31. Hash Generator — Generate MD5, SHA-1, SHA-256, and other cryptographic hashes from text input.
32. Color Palette Generator — Create harmonious color palettes from a base color.
33. Favicon Generator — Create favicons from images in all required sizes.
34. robots.txt Generator — Build robots.txt files with proper directives.
35. .htaccess Generator — Generate Apache redirect rules and configuration snippets.
36. Sitemap Generator — Create XML sitemaps for search engine indexing.
37. Meta Tag Generator — Generate HTML meta tags for SEO and social media sharing.
38. QR Code Generator — Create QR codes for URLs, text, Wi-Fi credentials, and contact information.

Converters

Move data between formats without writing throwaway scripts.

39. JSON to YAML — Convert JSON objects to YAML format and back.
40. JSON to CSV — Flatten JSON arrays into CSV format for spreadsheet import.
41. CSV to JSON — Convert CSV data into JSON arrays or objects.
42. Markdown to HTML — Convert Markdown text to clean HTML.
43. SCSS to CSS — Compile SCSS syntax to standard CSS.
44. Timestamp Converter — Convert between Unix timestamps, ISO 8601, and human-readable dates.
45. Number Base Converter — Convert numbers between decimal, binary, octal, and hexadecimal.
46. Color Format Converter — Convert between HEX, RGB, HSL, and other color formats.

Image and Media Tools

Handle images without Photoshop.

47. Image Compressor — Reduce image file size with adjustable quality.
48. Image Resizer — Resize images to exact dimensions or by percentage.
49. Image Format Converter — Convert between JPEG, PNG, WebP, AVIF, and other formats.
50. SVG to PNG Converter — Rasterize SVG graphics at any resolution.
51. Screenshot to Code — Convert screenshots into HTML/CSS code.
52. Image Color Picker — Extract colors from uploaded images with hex and RGB values.
53. Sprite Sheet Generator — Combine multiple images into a single sprite sheet with CSS coordinates.

PDF Tools

Work with PDFs without Adobe Acrobat.

54. PDF Merger — Combine multiple PDF files into one document.
55. PDF Splitter — Extract specific pages from a PDF.
56. JPG to PDF Converter — Convert images to PDF documents.
57. PDF Compressor — Reduce PDF file size for easier sharing.

Text and String Tools

Manipulate text quickly.

58. Word Counter — Count words, characters, sentences, and paragraphs.
59. Diff Checker — Compare two blocks of text and highlight differences line by line.
60. Case Converter — Convert text between camelCase, snake_case, kebab-case, PascalCase, UPPER CASE, lower case, and Title Case.
61. String Escape/Unescape — Escape strings for use in JSON, HTML, SQL, and regular expressions.
62. Line Sorter — Sort lines alphabetically, numerically, or by length.
63. Duplicate Line Remover — Remove duplicate lines from a list.
64. Text to Slug — Convert titles and strings into URL-friendly slugs.

Network and Security Tools

Debug connectivity and inspect security configurations.

65. IP Address Lookup — Get geolocation and ASN information for any IP address.
66. DNS Lookup — Query DNS records (A, AAAA, MX, TXT, CNAME, NS) for any domain.
67. HTTP Header Inspector — View the HTTP response headers for any URL.
68. SSL Certificate Checker — Inspect a domain’s SSL certificate for expiration and configuration issues.
69. CORS Tester — Test Cross-Origin Resource Sharing headers for any endpoint.
70. Subnet Calculator — Calculate subnet ranges, broadcast addresses, and host counts from CIDR notation.

Math and Calculation Tools

Quick calculations without a spreadsheet.

71. Percentage Calculator — Calculate percentages, percentage changes, and percentage of a number.
72. Unix Timestamp Calculator — Convert between Unix timestamps and human-readable dates.
73. Byte Converter — Convert between bytes, kilobytes, megabytes, gigabytes, and terabytes.

How to Get the Most Out of These Tools

Bookmark Your Top Five

You probably use the same five to ten tools repeatedly. Bookmark them for instant access. If you format JSON daily, having the JSON Formatter one click away saves meaningful time over the course of a month.

Choose Client-Side Tools for Sensitive Data

When working with production data, API keys, or credentials, use tools that process data locally. The tools on UtilityDocker run in your browser — nothing is sent to a server. This matters when you are decoding a JWT from production with the JWT Decoder or testing a regex against real user data with the Regex Tester.

Chain Tools Together

Many tasks involve multiple steps. Format JSON, then validate it. Decode a JWT, then Base64-decode a field within the payload. Convert a timestamp in an API response, then calculate the time difference. Keeping a suite of tools in your bookmarks bar turns your browser into a comprehensive development workbench.

Use Browser DevTools Too

Online tools complement browser DevTools — they do not replace them. The Network tab, Console, Elements panel, and Performance profiler remain indispensable. Online tools fill the gaps for tasks like formatting a JSON payload from a cURL response, testing a regex before embedding it in code, or decoding a Base64 string from a log file.

Conclusion

The 73 tools above cover the vast majority of quick tasks developers encounter daily. None of them require installation, accounts, or payment. Bookmark the ones most relevant to your stack, and you will spend less time on mechanical tasks and more time building the things that matter.

Start with the essentials: the JSON Formatter for daily data work, the Regex Tester for pattern matching, the JWT Decoder for authentication debugging, and the SQL Formatter for query readability. From there, explore the rest as your projects demand.