Skip to content
DevToolsCave

    All tools

    Browse every free, browser-based developer tool on DevToolsCave: converters, encoders and decoders, and generators. No sign-up, no tracking, no uploads.

    Converters

    Tools that translate a value from one representation into another without changing what it means — a Unix timestamp into a date, for example. The usual failure mode is ambiguity about units or timezone, so these tools show their assumptions rather than hiding them.

    Epoch Converter

    Convert Unix timestamps to and from human-readable dates.

    Encoding & Decoding

    Encoding makes data safe to transport; it is not encryption and provides no secrecy. These tools decode in your browser, which matters because the values involved — tokens, credentials, payloads — are often things you should never paste into a website that uploads them.

    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.

    Generators

    Tools that produce new values on demand: identifiers, random numbers, sample data. Where randomness matters, these use the browser's cryptographic random source rather than Math.random, so the output is suitable for identifiers and not just for demos.

    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.

    How these tools work

    Every tool listed above runs as JavaScript inside your own browser tab. When you paste a JSON Web Token or a base64 string, the decoding happens on your device and the result never travels across the network — there is no API call behind these tools, and no server that could log what you entered even if it wanted to. You can verify this yourself: open your browser's developer tools, switch to the Network tab, and use any tool on this site. You will not see a request go out.

    That design has a practical consequence beyond privacy. Because there is no round-trip, results appear as you type rather than after a submit, there are no rate limits or usage quotas, and the tools keep working when your connection does not. The site is installable as an app, and once installed the whole catalog is available offline.

    Why paste-into-a-website is a real risk

    Developer utilities are a soft target precisely because the values people paste into them are sensitive by nature: session tokens, API keys, internal identifiers, customer data pulled from a log line. A tool that posts your input to a backend has, at minimum, put that value into someone else's request logs. The convenient habit — search for "jwt decoder", click the first result, paste — is how credentials end up on servers nobody audited.

    The honest answer is not to trust a promise on a marketing page, including this one. Prefer tools that decode locally, check the network tab when it matters, and treat any token you have pasted into an unknown site as compromised.

    What gets added next

    The catalog is deliberately small and growing slowly: each tool is unit-tested against its edge cases before its interface exists, because a utility that is quietly wrong on unusual input is worse than no utility at all. Planned additions include a URL encoder/decoder, hash generators, a JSON formatter and validator, a color format converter, a cron expression parser, and a text diff viewer.