Developer tools, all in one cave.
Fast, free, and private. Every tool runs in your browser — no sign-up, no tracking, and nothing you paste ever leaves your device.
There is no server to send it to. Here's how to check that in thirty seconds →
We work out what it is and take you to the right tool. Nothing is sent anywhere.
Nothing leaves the cave.
Tools compute locally, so there is nothing to upload and nothing to log. How you can check
Works offline
Install it, and the whole cave comes with you — which is only possible because the work was never happening elsewhere.
No sign-up, ever
Every tool is free and instantly usable. No account, no email, no quota.
JSON
JSON Formatter & Validator Featured
Format, minify and validate JSON without your numbers changing.
JSON to YAML
Convert JSON to YAML, with every value a real YAML reader would misread quoted.
JSON to CSV
Flatten JSON into spreadsheet columns, with long numbers intact.
CSV to JSON
Turn spreadsheet rows into JSON without retyping your values.
XML to JSON
Convert XML to JSON with the mapping rules stated, not hidden.
JSON to XML
Turn JSON into well-formed XML, with attributes and indentation.
Time & Date
Cron Expression Generator Featured
Build a cron expression for any scheduler, or paste one to see what it runs.
Date Format Generator Featured
Pick the fields you want, get the format string for any language.
Epoch Converter
Paste any timestamp — seconds, ms, µs, ns, ISO, or SQL — and see what it is.
World Clock Featured
Compare time zones on one shared timeline, with daylight at a glance.
Encoding & Decoding
JWT Decoder
Decode a JSON Web Token's header and payload instantly.
Base64 Encoder/Decoder
Encode text to base64 or decode base64 back to text.
URL Encoder / Decoder
Percent-encode or decode a URL, with proof the result round-trips.
URL Parser
Split a URL into its parts, decode every query parameter, and rebuild it.
Generators
UUID Generator
Generate RFC 4122 v4 UUIDs, one at a time or in bulk.
Random Number Generator
Generate random integers or decimals in a custom range.
Lorem Ipsum Generator
Placeholder text with an exact word/character/byte count, a seed you can replay, and output already wrapped in HTML, Markdown or JSON.
Text & Data
Table Workbench Featured
Paste a table, get sums and averages instantly — with nothing mangled.
Universal Regex Tester & Builder Featured
Test and build regex for Java, Python, Go, JavaScript, .NET, PHP and grep — free, in your browser.
Case Converter
Convert text between 19 cases — sentence, Title, camelCase, snake_case and more — with an acronym-safe tokenizer and a receipt for every change.
Slug Generator
Turn a title into a URL-safe slug with a named transliteration convention, a change table for every substitution, and a loud error instead of a silent empty string.
Logs & Debugging
Config & Infra
Properties to YAML Featured
Convert application.properties to YAML, with every changed value reported.
YAML to Properties Featured
Convert application.yml to properties, with every value it cannot recover named.
YAML to JSON New
Convert YAML to JSON, with anchors, merges and tags mapped or refused by name.
Security & Hashing
Password Generator Featured
Generate a strong password with real entropy and per-algorithm crack times — or one that matches a site's own rules.
Hash Generator
Every hash of your text at once — MD5 through BLAKE3 — computed twice and cross-checked against the browser's own crypto.
File Checksum
Checksum any file — even multi-gigabyte ones — with a measured progress bar and a working cancel, entirely in your browser.
HMAC Generator
HMAC-sign or verify a message, with real key-encoding support and the actual Stripe, GitHub, Slack and Shopify signing schemes — not just HMAC(secret, body).
Color & Design
Color Converter
Convert HEX, RGB, HSL, OKLCH, CMYK and more — and see which values survive the trip back.
Color Contrast Checker
Check any foreground/background pair against WCAG AA and AAA, composite alpha against a backdrop, and get a same-hue fix that passes.
Color Scale Generator
Turn one seed color into a 50–950 tint/shade ramp with even OKLCH steps, an explicit chroma taper, and a contrast matrix.
CSS Gradient Generator
Build linear, radial and conic CSS gradients, and see the same stops fade through grey in sRGB or stay vivid in OKLCH.
OKLCH Gradient Generator New
Author gradients in L, C and H, and see the lightness curve, the chroma against the gamut ceiling and the hue arc the CSS is hiding.
Numbers & Bits
Number Base Converter
Convert between any base 2-36 with arbitrary size, an exact fractional half, and the width and sign always stated.
Bitwise Calculator
AND, OR, XOR, NOT and shifts at any width up to 64-bit and beyond, with a per-bit diagram and a shift receipt.
IEEE 754 Converter
Decimal, hex or binary in — sign, exponent and mantissa out, with the exact stored value and the rounding error against what you typed.
Web & Markup
CSS Minifier
Minify CSS without losing nested rules, custom properties or browser hacks.
HTML Minifier
Minify HTML without collapsing the whitespace that changes how your page looks.
JavaScript Minifier
Minify JavaScript with real mangling, powered by a vendored, hash-pinned Terser.
Cubic Bezier Generator New
Drag a cubic-bezier curve and see the CSS, Tailwind and linear() output alongside the Penner presets and their measured fit error.
Why another developer tools site?
Because the existing ones are interchangeable. You search for a JWT decoder, click a result, paste your token, get your answer, and forget where you were — and next week you search again. The tools work, but nothing about them earns a second visit, and it is never obvious what else the site can do.
DevToolsCave is built on the opposite assumption: that the catalog is the product. Every tool links to related tools, a command palette (Ctrl + K) reaches any of them from any page, and the box at the top of this page will identify what you paste and send you to the right tool without you having to know its name.
Everything runs in your browser
These tools are JavaScript that executes on your device. Nothing you type or paste is sent anywhere, because there is no backend to send it to — a distinction that matters most for exactly the values developers paste into utilities like these: access tokens, API keys, internal identifiers, rows copied out of a production log.
You do not have to take that on trust. Open your browser's developer tools, watch the Network tab, and use any tool here; no request leaves the page. The same property is what lets the site work with no connection at all once installed.
Correctness before features
A utility that is quietly wrong on unusual input is worse than no utility, because you cannot tell which answers to trust. Every tool's logic is unit-tested against its awkward cases — empty input, malformed input, multi-byte characters, boundary values — before its interface is built, and invalid input clears the result rather than leaving a stale one sitting next to it looking correct.
That principle costs features, deliberately. The
time zone converter will not recommend a meeting slot,
because it cannot know anyone's working hours — it shows every city at the instant you pick
and lets you decide. The
JWT decoder reads a token's claims but says plainly that
it cannot verify the signature without the key. The
table calculator has no formula bar, because almost
nobody typing =SUM wants a formula — they want the number once. Being clear
about the edge of what a tool knows is worth more than a confident guess.