Free tools for developers

Format and convert JSON, YAML, CSV and SQL, decode JWTs and Base64, test regular expressions, and make UUIDs, hashes and favicons. All in the browser.

Illustration for Free tools for developers

30 tools

JSON FormatterPaste JSON to check that it's valid, then format it with clear indentation or minify it to one line. If something is wrong, you see what and, in most browsers, the line and column. Copy the result or download it as a .json file.
Markdown to HTMLType or paste Markdown and get clean HTML instantly, with a live preview. Tables, code blocks, strikethrough and links are supported, and unsafe code is removed. Copy the HTML or download it as a complete .html page.
UUID GeneratorGenerate random version 4 UUIDs or time-ordered version 7 UUIDs (GUIDs), one at a time or up to 1,000 at once, in lowercase or uppercase, with or without hyphens or braces. Copy them all or download a .txt file. They're made on your device with a secure random source.
Password GeneratorMake a strong, random password in one click: choose a length from 8 to 128 characters and which of lowercase, uppercase, numbers and symbols to use, then copy it. Every character is picked with your device's secure random source, and the password is never sent anywhere.
Image to Base64Turn a JPG, PNG, WebP, GIF, SVG or ICO image into Base64 text, ready to paste as a data URI, an HTML <img> tag or a CSS background. Copy it or download it as a .txt file. Your image stays on your device and is never uploaded.
Favicon GeneratorMake a favicon for your website from one to three letters, an emoji or your logo, and download favicon.ico, the PNG sizes, the iPhone and Android home-screen icons and a web manifest in one ZIP, with the code to paste into your site. Your files are made on your device.
CSS Gradient GeneratorDesign a linear, radial or conic gradient with 2 to 8 colour stops, see it live, and copy the CSS background code. You can also download the gradient as a PNG image in HD, 4K, square, story or banner sizes.
HEX to RGB Color ConverterConvert HEX to RGB, or RGB to HEX, as you type: paste a colour code in any format and get HEX, RGB, HSL, HSV and CMYK at once, each with a copy button. Set the opacity for 8-digit HEX and rgba(), and see how readable white or black text is on the colour.
Color Contrast CheckerEnter a text colour and a background colour to get the WCAG contrast ratio and pass or fail results for AA and AAA, for normal text, large text and buttons or icons. If it fails, click the closest colour that passes.
Color Palette GeneratorGenerate a five-colour palette with one press of the space bar, lock the colours you like, or build a colour scheme from your own base colour: analogous, complementary, triadic and more. See 11 shades of each colour and export as CSS variables, Tailwind, JSON or HEX.
Number Base ConverterConvert numbers between binary, decimal, hexadecimal and octal, or any base from 2 to 36. Type in any box and the others update as you type, exactly, for whole numbers of any size, with negatives shown in two's complement too.
Text ComparePaste two versions of a text to see exactly what changed: removed text in pink, added text in green, side by side or inline. Compare by lines, words or characters, and ignore capitals or extra spaces when they don't matter.
URL Slug GeneratorTurn a title or any text into a clean, lowercase URL slug like "my-first-blog-post". Accents are converted (café becomes cafe), symbols are removed, and you can drop small words, set a maximum length or make slugs for a whole list of titles at once.
Lorem Ipsum GeneratorGenerate lorem ipsum placeholder text as paragraphs, sentences, words or list items, starting with the classic "Lorem ipsum dolor sit amet" if you like. Copy it as plain text or as ready-made HTML for web pages and mock-ups.
AI Token CounterPaste a prompt or document to count its tokens as you type: exact counts for GPT-5, GPT-4.1, GPT-4o and GPT-4, plus estimates for Claude and Gemini, and how much of each model's context window it fills. Your text never leaves your device.
Base64 Decode and EncodeDecode Base64 to readable text, or encode text to Base64, as you type. Accents and emoji (UTF-8) and URL-safe Base64 work, and you can turn a file of up to 50 MB into Base64 or a data URL, or save decoded Base64 back as a file.
Cron Expression GeneratorBuild a cron expression by picking how often a job should run, or paste one to see it explained in plain English with its next 8 run times. Uses the standard five-field crontab format, with common schedules one click away.
CSV to TSV ConverterConvert comma-separated (CSV) data to tab-separated (TSV), or TSV back to CSV, as you paste. Quoted values, commas inside values and line breaks are handled correctly, so nothing shifts into the wrong column. Semicolon and pipe-separated files work too.
Hash GeneratorGet the MD5, SHA-1, SHA-256, SHA-384 and SHA-512 hash of any text as you type, or the checksum of a file up to 500 MB, and compare it with the one a download page lists. All five hashes appear at once.
HTML Entity Encoder and DecoderEncode text into HTML entities so it shows safely on a web page, or decode entities like &, é and é back into readable text, as you type. Choose how much to encode and whether to use named or numbered entities.
JSON to CSV ConverterConvert a JSON array into a CSV file you can open in Excel or Google Sheets, or turn CSV back into JSON, as you paste. Nested objects become columns like user.name, and a preview shows the first rows as a table.
JSON to XML ConverterConvert JSON to well-formed XML, or XML to JSON, as you paste. Attributes, repeated elements and text are kept intact, you choose the indent and root element, and errors tell you where the XML needs fixing.
JSON VisualizerPaste or open a JSON file up to 20 MB to explore it as a collapsible tree or as a graph of connected boxes. Search keys and values, copy the path to any field, and see exactly where invalid JSON breaks.
JWT DecoderPaste a JSON Web Token to read its header and payload as formatted JSON, see the issued, not-before and expiry times as dates, and check at a glance whether it has expired. The token is decoded on your device and never sent anywhere.
Regex TesterTest a regular expression against your text and see every match highlighted as you type, with a table of capture groups (named ones too) and a live find-and-replace preview. It follows JavaScript regex rules, and a pattern that runs too long is stopped instead of freezing the page.
SQL FormatterPaste messy SQL and get a clean, indented query in one click, or minify it onto one line. Choose your dialect (PostgreSQL, MySQL, SQL Server, Oracle, BigQuery, Snowflake and more), keyword case and indent, then copy or download the result.
String Escape and UnescapeEscape text so it fits safely inside a JSON, JavaScript, CSV, SQL, regular expression or XML string, or turn escaped text like \n and \" back into plain text. The result updates as you type, ready to copy.
Unix Timestamp ConverterConvert a Unix timestamp to a readable date and time in any time zone, or turn a date into a timestamp in seconds or milliseconds. Seconds, milliseconds, microseconds and nanoseconds are detected automatically, and you can convert up to 1,000 timestamps at once.
URL Encode / DecodeEncode text for a URL or decode %20-style percent-encoding back to readable text, as you type. Paste a full link to see its query parameters listed and decoded, and choose whether spaces become %20 or +. Nothing leaves your device.
YAML to JSON ConverterConvert YAML to JSON or JSON to YAML as you type, with a clear error and line number when the YAML isn't valid. Anchors, aliases, multi-line strings and multiple documents are supported, and you can open a file and download the result.

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