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Best free developer tools

Best free developer tools for JSON, JWT, Base64, passwords, UUIDs, QR codes, and hashes—pros, cons, and when to use each Utilnivo utility.

7 free tools in this guide — pick one below to get started.

All tools in this guide(7)

Open a tool to calculate, convert, or edit — no signup required.

Which tool for each task

Pick the job you need to finish first. Each card lists trade-offs and links straight to the Utilnivo tool—free, no account required unless a tool page notes temporary server processing.

Pretty-print or validate JSON

Use JSON Formatter or JSON Validator.

Pros

  • Instantly formats minified API responses for debugging.
  • Catches trailing commas and invalid tokens before deploy.
  • Runs locally—payloads are not sent to a server.

Cons

  • Very large JSON can slow low-memory devices.
  • Uses JavaScript JSON semantics (not JSON5).

When to choose this: Use JSON Formatter when reading logs or config diffs. Pair with JSON Validator in CI-style manual checks.

Open JSON Formatter

Inspect a JWT or bearer token

Use JWT Decoder.

Pros

  • Shows header, payload, exp, and custom claims.
  • Helpful for OAuth and API gateway debugging.
  • Quick decoding for inspection on your device.

Cons

  • Does not verify signatures—never treat decoded tokens as trusted.
  • Production secrets should not be pasted on shared machines.

When to choose this: Decode test tokens to compare expiry and audience fields before updating your app's security rules.

Open JWT Decoder

Encode or decode Base64 text

Use Base64 Encoder & Decoder.

Pros

  • Handles data URLs, MIME snippets, and API fixtures.
  • Clear errors on invalid padding.
  • Local processing only.

Cons

  • Base64 is not encryption—anyone can decode the string.
  • Binary files pasted as text may corrupt—use file checksum tools instead.

When to choose this: Use when debugging JWT segments, email headers, or JSON fields that embed Base64 blobs.

Open Base64 Encoder & Decoder

Generate a strong random password

Use Strong Password Generator.

Pros

  • Uses strong random generation.
  • Configurable length and character sets.
  • Exclude ambiguous characters for legacy systems.

Cons

  • Generated secrets are visible on screen—copy into a vault immediately.
  • Sites with short max lengths need shorter outputs.

When to choose this: Spin up staging admin passwords or Wi-Fi keys you will store in a password manager, not chat logs.

Open Strong Password Generator

Generate UUIDs for test data

Use UUID Generator.

Pros

  • Supports random v4 and time-ordered v7.
  • One-click copy for seed scripts.
  • No server round trip.

Cons

  • Collision safety still needs database unique constraints.
  • Not a substitute for platform session-token formats.

When to choose this: Use v7 when sortable IDs help logs; v4 for opaque identifiers in fixtures.

Open UUID Generator

Create a QR code for a URL or Wi-Fi string

Use QR Code Generator.

Pros

  • Encodes URLs, vCards, and Wi-Fi join strings.
  • Adjustable error correction for logo overlays.
  • Download PNG for print or slides.

Cons

  • A single typo makes the code unscannable—test on a real phone.
  • Very long URLs need shortening for reliable print scans.

When to choose this: Generate campaign QR codes after you finalize the UTM link in a marketing workflow.

Open QR Code Generator

Hash text for checksums or fixtures

Use Hash Generator or File Checksum Calculator.

Pros

  • SHA-256 and related digests for integrity checks.
  • Instant diff when a single character changes.
  • Local-only for string input.

Cons

  • Not for password storage—use bcrypt or Argon2 in apps.
  • MD5/SHA-1 are legacy only for new security designs.

When to choose this: Hash release-note strings or config snippets. Use File Checksum for downloaded binaries.

Open Hash Generator

Overview

Developers search for free utilities when debugging an API response, decoding a bearer token, or spinning up staging credentials—not to install another desktop app. This page matches each task to a Utilnivo browser tool with clear pros, cons, and when that option wins.

These utilities run locally unless noted otherwise. Secrets you paste are visible on screen—use staging tokens only and copy generated passwords into a vault immediately. None of these tools verify JWT signatures or replace your platform’s crypto libraries.

For structured debugging sessions, open the JWT workflow linked below—it orders decode, JSON format, and Base64 steps the way teams actually troubleshoot auth issues.

How to choose

  • Minified API JSON → JSON Formatter or JSON Validator.
  • Bearer token claims → JWT Decoder.
  • Encoded segment → Base64 Encoder.
  • Staging password → Password Generator.
  • Fixture IDs → UUID Generator.
  • Campaign QR → QR Code Generator.
  • Checksum string → Hash Generator or File Checksum.

Frequently asked questions

Are inputs sent to Utilnivo servers?

JSON, JWT, Base64, password, UUID, and hash tools run on your device. Do not paste production secrets on shared machines.

Can JWT Decoder verify signatures?

No. It inspects structure for debugging. For real security, verify tokens in your own app with the correct keys.

Which hash for passwords?

None of these for user passwords—use bcrypt, scrypt, or Argon2 in application code. Hash Generator is for integrity checks.

Step-by-step workflows (2)

Multi-step guides that chain tools from this topic—follow numbered steps instead of guessing tool order.

View all workflows

Related topic guides