Free developer and learning tools
Format code, compare text, decode tokens and generate IDs, plus a typing test, maths drills and an equation editor.
These are the small utilities you reach for a few times a week and never want to install: format a snippet, read a token, work out what a cron expression actually does, diff two config files, generate some identifiers. Alongside them are three tools for practice rather than production - a typing test, maths drills and an equation editor.
The Code Formatter runs real Prettier - the same formatter your editor uses - over JavaScript, TypeScript, JSON, CSS, SCSS, Less, HTML, Markdown, YAML and GraphQL. The Diff Checker compares two blocks of text side by side, and with Treat as JSON ticked it compares JSON structurally, so reordered keys and indentation changes do not show up as differences. The JWT Decoder is the one where running locally is not a nicety: a token is a working credential, and this one decodes it in the page and can verify an HS256, HS384 or HS512 signature without the secret leaving your machine either.
The Cron Explainer translates a crontab expression into English and lists the next five times it will fire, which catches the mistakes that reading the five fields again does not. The UUID and ID Generator produces UUID v4 and v7, Nano IDs and hex tokens from your browser's cryptographic random source, in bulk, and the File Hash Checker works out MD5, SHA-1, SHA-256 and SHA-512 checksums of a file of any size and tells you whether it matches the one a download page published.
The Typing Speed Test measures words per minute and accuracy, with a heatmap of the letters you get wrong, and the Equation Editor builds mathematical notation from a palette of symbols, a formula library or LaTeX, pasting into Word as an equation you can edit. Math Drills generates timed arithmetic sets for primary school, and is the one tool here that uses the server: the questions are made and your answers marked by an API on this site, and nothing is stored. Everything else runs in your browser. All free, no sign-up.
- Code FormatterPrettier online: format JS, TypeScript, CSS, HTML, JSON, Vue, Markdown, YAML and GraphQL with every option or your .prettierrc. Runs locally, never uploaded.
- Diff CheckerCompare two texts, code files or JSON documents side by side, with changed lines and words marked. Ignore whitespace or case. Nothing is uploaded.
- JWT DecoderDecode a JSON Web Token's header, payload and expiry, and verify an HS256, HS384 or HS512 signature in your browser, with no network requests.
- Cron ExplainerPaste a cron expression and get plain English, a field-by-field breakdown, and the next five run times. Free, instant and entirely in your browser.
- File Hash CheckerCheck a file's MD5, SHA-256, SHA-512, SHA-3, BLAKE3 or CRC32 hash, even a multi-gigabyte download, or verify a whole SHA256SUMS list. No upload.
- PCAP ViewerOpen a .pcap or .pcapng capture without Wireshark. See every packet, filter by protocol or address, and read each one decoded. Nothing uploaded.
- UUID & ID GeneratorGenerate random IDs online: UUID v4, v7 and v1, ULIDs and Nano IDs with your own characters, up to 100,000 at once, and check any UUID. Nothing is uploaded.
- Equation EditorBuild equations from symbols, a formula library or LaTeX, then paste them into Word as editable equations or Google Docs as images, or save SVG or PNG.
- Typing Speed TestA timed typing test with live words per minute, accuracy, and a heatmap of the letters you mistype most. Runs entirely in your browser.
- Timed Math DrillsTimed math drills for addition, subtraction, times tables and division: 60-second sprints or worksheets, instant marking, printable PDF. Free, no sign-up.