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15 free tools

Free Developer Tools

The converters, encoders and testers you reach for every day while coding — and your data never leaves your browser.

JSON FormatterPaste JSON to format, validate, minify or explore it as a tree — errors are pinpointed to the exact line and column.Base64 Encode/DecodeEncode text or files to Base64 and decode Base64 back to text or a downloadable file — UTF-8 safe, with a URL-safe option.URL Encoder/DecoderPercent-encode or decode text for URLs, and break any URL into its parts with editable query parameters.Hash GeneratorGenerate MD5, SHA-1, SHA-256, SHA-384 and SHA-512 hashes or an HMAC-SHA256 of any text or file, and verify a checksum in one step.Unix Timestamp ConverterConvert Unix epoch timestamps to readable dates and back, with the current timestamp updating live.Regex TesterWrite a regular expression and see matches highlighted live, with capture groups, a replace preview and ready-made patterns.Color ConverterEnter a color in any format — HEX, RGB, HSL, HSV, CMYK, OKLCH or a CSS name — and get every other format, plus shades and matching colors.Contrast CheckerCheck if your text and background colors meet WCAG AA and AAA contrast requirements, and get the nearest passing color if they don’t.Binary TranslatorTranslate text to binary code and back, view the same bytes as hex, octal or decimal, and convert numbers between bases.UUID GeneratorGenerate cryptographically random v4 or time-ordered v7 UUIDs in bulk, and decode any UUID to see its version, variant and timestamp.JWT DecoderDecode the header and payload of any JSON Web Token, see when it expires, and verify HMAC signatures — without the token leaving your browser.CSV to JSON ConverterConvert CSV to JSON and JSON to CSV in your browser, with automatic delimiter detection, correct handling of quoted fields and optional type inference.Markdown to HTMLWrite or paste Markdown and get clean HTML with a live preview — including GitHub-style tables, task lists and fenced code — or convert HTML back to Markdown.Cron Expression GeneratorBuild a cron schedule field by field, or paste an existing expression to see what it means in plain English and when it will run next.CSS Gradient GeneratorDesign linear, radial and conic gradients visually with draggable color stops, then copy ready-to-use CSS or a Tailwind class.

Data formats and encoding

The JSON formatter pretty-prints, validates and pinpoints the line of a syntax error. The CSV to JSON converter reshapes spreadsheet data for APIs, and the Markdown to HTML converter turns README files or blog drafts into HTML. Base64, URL encode/decode and the binary translator fix the encoding problems that come up when moving data between systems. Remember that Base64 is an encoding, not encryption: anyone can decode it in seconds, so never use it to hide secrets.

Debugging and testing

The JWT decoder makes a token’s header and payload readable and shows when it expires; because decoding happens in the browser, the token is not sent to any server. The regex tester highlights matches live against your sample text. The Unix timestamp converter turns log timestamps into readable dates and back, and the cron expression generator lists the next run times of a schedule so you can catch a wrong field before it reaches production.

IDs, hashing and front-end helpers

The UUID generator creates unique identifiers for database records and tests, and the hash generator computes MD5, SHA-1 and SHA-256 digests. For storing passwords, use a slow algorithm such as bcrypt or Argon2 instead of MD5 or SHA-1. On the front end, the color converter translates between HEX, RGB and HSL, the contrast checker tests color pairs against WCAG accessibility ratios, and the CSS gradient generator produces ready-to-paste CSS code.

Related guides

Base64 and URL encoding: what they are and when to use themBase64 turns binary data into plain text; URL encoding makes text safe to put in a web address. Neither hides anything. Here is how both work, with worked examples and pitfalls.Colour contrast and WCAG: how to make text readable for everyoneWCAG Level AA requires a contrast ratio of at least 4.5:1 for normal text and 3:1 for large text and UI components. Here is what that means, how it is calculated and how to fix failing colours.JSON basics: syntax, common errors and how to fix themJSON is a strict text format for structured data. Most 'invalid JSON' errors come from a handful of mistakes, such as trailing commas and single quotes. Here is the syntax and how to fix them.Regex cheat sheet: the syntax you need, with practical examplesRegular expressions describe text patterns. A small core of syntax covers most real tasks, from validating a postcode to extracting dates from logs. Here it is, with examples you can test.How to create a strong password you can actually live withLength beats complexity, uniqueness beats cleverness, and a password manager beats your memory. Here's what current guidance actually recommends.Unix timestamps explained: epoch time, time zones and cronA Unix timestamp is the number of seconds since 1 January 1970 UTC. It is time-zone-free, easy to compare and everywhere in software. Here is how to read, convert and schedule with it.

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