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60+ free developer tools that run entirely in your browser — JSON formatter, JWT decoder, Base64, diff checker, regex tester, hash generator and more. No upload, no sign-up, completely private.

JSON & Data

  • JSON Formatter
  • JSON Minifier
  • JSON Validator
  • JSON to CSV
  • CSV to JSON
  • JSON to YAML

Encode & Decode

  • Base64 Encode / Decode
  • Base64 to Image
  • Image to Base64
  • URL Encode / Decode
  • HTML Entity Encoder
  • JWT Decoder

Text Tools

  • Text Diff Checker
  • Case Converter
  • Word & Character Counter
  • Slug Generator
  • Remove Duplicate Lines
  • Sort Text Lines

Generators

  • UUID Generator
  • Password Generator
  • Lorem Ipsum Generator
  • QR Code Generator
  • Random Number Generator
  • NanoID Generator

Popular Guides

  • How to Format and Pretty-Print JSON (Without Breaking It)
  • How to Minify JSON and Shrink Your API Payloads
  • How to Validate JSON and Pinpoint the Exact Syntax Error
  • How to Convert JSON to CSV for Excel and Google Sheets
  • How to Convert CSV to JSON (With Proper Header Detection)
  • All guides →

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  • UUID Generator

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  • 100% in your browser
  • Zero uploads
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© 2026 filemarkr. Designed & developed by Naved Naik.  All processing happens locally in your browser.

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Random Number Generator

Generate random numbers in any range, with unique and sorted options.

100% private Instant, in-browser Read the guide
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Random Number Generator

The random number generator creates random integers in any range you define, right in your browser. Whether you need a single random pick, a batch of test data, a raffle winner, or a seed value for a script, you set the minimum and maximum, choose how many values to produce, and get them instantly. Options for unique (no repeats) and sorted output make it easy to build clean sample sets or lottery-style draws without writing a single line of code.

How it works

Everything runs locally using your browser's built-in JavaScript random functions. You enter a range and a count, toggle unique or sorted if you need them, and the results appear immediately, ready to copy with one click. Because the work happens on your own device, there are no network requests, no queues, and no rate limits. It behaves the same on desktop and mobile, and keeps working offline once the page has loaded.

Common use cases

  • Generate sample or seed data for testing and QA.
  • Pick a random winner for a giveaway or a standup rotation.
  • Produce non-repeating numbers for lottery-style draws.
  • Create random indexes to shuffle or sample a dataset.

Need other kinds of random values? Pair this with the UUID Generator for unique identifiers, the NanoID Generator for compact URL-safe IDs, or the Password Generator for secure random strings.

Private by design

No ranges, counts, or results ever leave your device. There is no upload, no account, and no logging — the tool is completely free and runs entirely client-side, so whatever you generate stays with you.

Frequently asked questions

No. They come from JavaScript's Math.random, which is ideal for testing, sampling, and draws but not for security tokens. For secret values, use a crypto-grade source or the Password Generator.

Related tools

UUID Generator

Generate v4 and v1 UUIDs in bulk, ready to copy or download.

Password Generator

Create strong, random passwords with full control and a strength meter.

Lorem Ipsum Generator

Generate placeholder paragraphs, sentences or words for mockups.

QR Code Generator

Create a downloadable QR code from any link or text, right in the browser.