OnlineDeveloperTool
8 tools

UUID, JWT and Hash Generators

These tools create or check the identifiers and digests that show up in everyday development. The UUID generator makes random version 4 UUIDs in bulk, and the validator and parser check a UUID's format, version and variant. The JWT generator signs a test token with HS256, which is handy for trying an API or a decoder.

The hash tools return the SHA-256, SHA-512 or MD5 digest of the text you type. Hashes are one-way and are not encryption. MD5 is only suitable for non-security checksums, and no plain hash is a safe way to store passwords.

Which generators & hashes tool do you need?

  • You need unique IDs for test data or keys: UUID Generator. Generate 1 to 100 random v4 or v7 UUIDs at once.
  • You are not sure a UUID string is valid: UUID Validator. Check the format, or use the UUID parser to read its version and variant.
  • You need a quick test token for an API: JWT Generator. Sign a JSON payload with HS256 and a test secret. Do not use production secrets.
  • You need a checksum or digest of some text: SHA-256 Generator. SHA-256 is a good default. Use the SHA-512 page for a longer digest, or MD5 only for non-security checksums.

All generators & hashes

More developer tool categories

onlinedevelopertool.com is a collection of 54 free, browser-based utilities for the small jobs that interrupt real work: formatting a JSON response, decoding a token, converting a timestamp, generating a UUID or checking a hash. Each tool has its own page with a short explanation, a worked example and answers to common questions, so you can use it and learn what it does at the same time.

There is no account to create and nothing to install. Tools run in your browser, so the text you paste is processed on your own device. The one exception is the Website Status Checker, which sends a request from your browser to the address you enter.

Three steps: paste your input, click the tool, copy the result, all inside your browser
Popular developer utilities: JWT decoder, UUID generator, Base64 decoder, SHA-256 hash, regex tester and timestamp converter

What you can do here

  • JSON Tools

    Format, validate, beautify and minify JSON, generate C#, TypeScript, Java, Python, Go, PHP and Kotlin models from it, or convert between JSON, YAML and CSV.

  • Encoders & Decoders

    URL, Base64 and HTML encoding and decoding, plus a JWT decoder for reading token claims.

  • Generators & Hashes

    Generate UUIDs and JWTs, validate UUIDs, and create MD5, SHA-256 and SHA-512 hashes.

  • Web Tools

    Timestamps, color codes, query strings and cron expressions - the small things web work keeps throwing at you.

  • Text & Data

    Format XML and YAML, count text, change case, make slugs, test regex, diff two texts and convert number bases.

  • Website Checking

    Check whether a website or URL is reachable from your browser.

Quick developer reference

  • JSON

    Keys and strings must use double quotes, and trailing commas and comments are not allowed. Those are the three most common reasons a payload fails to parse.

    Validate JSON

  • JWT

    A JSON Web Token is three Base64URL parts joined by dots: header, payload and signature. Decoding shows the claims but does not prove the token is genuine; only signature verification does.

    Decode a JWT

  • Base64

    Base64 is an encoding, not encryption. Anyone can reverse it, and it makes data roughly one third larger, so never use it to hide secrets.

    Decode Base64

  • UUID

    A version 4 UUID is made of random bits and written as 8-4-4-4-12 hexadecimal characters. Collisions are astronomically unlikely, which is why they work well as identifiers.

    Generate a UUID

  • Timestamps

    A Unix timestamp counts time since 1 January 1970 UTC. Ten digits usually means seconds and thirteen digits usually means milliseconds.

    Convert a timestamp

  • Hashes

    MD5 is fine for quick checksums but is not safe for security. Prefer SHA-256 or SHA-512, and remember that hashing is one-way and is not encryption.

    Create a SHA-256 hash

Missing a tool you need? Visit the contact page and tell us what you reach for most often. You can also browse every tool or read the About page to see how the site is built and what it does with your data.