Developer Tools
13 tools, free and without ads.
The everyday utilities of building software: format this, decode that, work out what this expression actually matches. Individually small, collectively a large share of the tabs a working developer has open.
There is a specific reason to care where these run. Pasting a JWT, a config file or a production payload into a random online decoder hands that data to whoever operates it — and the useful ones are exactly the tools you reach for while debugging something sensitive. Everything here executes locally, and works with the network off.
Every tool in Dev
Parse cron expressions into plain English, preview the next scheduled run times, and browse common patterns.
Calculate IPv4 subnet details from CIDR notation — network address, broadcast, host range, mask, and subnet splitting.
Decode, verify and sign JSON Web Tokens. Inspect header, payload and claims, check a signature with HS/RS/ES algorithms, or build and sign a new token.
Convert between CSV and JSON formats. Handles RFC 4180 quoting, custom delimiters, type inference, and table preview.
Test and debug regular expressions with live match highlighting, capture group extraction, and flag toggles.
Generate SHA-256, SHA-384, and SHA-512 cryptographic hashes from text.
Compute a file’s SHA-256, SHA-384, SHA-512, SHA-1 or MD5 checksum and compare it against a published value. Nothing is uploaded.
Convert numbers between binary, octal, decimal, and hexadecimal.
Convert between Unix timestamps and human-readable dates. Live clock included.
Generate v4 (random), v5 (deterministic), and v7 (time-ordered) UUIDs.
Format and prettify JSON, or minify it for production. Validates JSON instantly.
Generate TypeScript interfaces or type aliases from pasted JSON. Merges mixed arrays, quotes awkward keys, and resolves name collisions.
Convert text between camelCase, PascalCase, snake_case, kebab-case, CONSTANT_CASE, Title Case, and more.
Reading, converting, and generating
Read something opaque — the JWT decoder, cron expression parser, regex tester and CIDR calculator all take an expression that is technically human-readable and tell you what it actually means. This is where a mistake is most expensive and hardest to see by eye: an off-by-one in a cron field or a subnet mask fails quietly and at the worst time.
Convert between shapes — CSV to JSON, JSON to TypeScript, number bases, Unix timestamps, case conversion. Mechanical transformations where the risk is not subtlety but volume.
Generate a value — UUIDs, hashes, file checksums. A checksum computed in your browser is computed on the actual bytes of your file, without an upload, which is the only way that check means anything for a file you would not want to share.
One caveat on the JWT tool — decoding a token shows you its claims, it does not verify them. A decoded payload is what the token says, not proof that anyone trustworthy said it.
Related categories
- Encoders and Decoders — Base64, URL and HTML escaping — filed separately because they are not only a developer's problem.
- Random Generators — Passwords and random values, when you need a secret rather than an identifier.
- Design and Colour Tools — Colour conversion and image compression, for the front-end end of the same job.