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filemarkr

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 →

Explore

  • All Tools
  • JSON Formatter
  • JWT Decoder
  • Diff Checker
  • UUID Generator

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Our Promise

  • 100% in your browser
  • Zero uploads
  • No sign-up, always free

© 2026 filemarkr. Designed & developed by Naved Naik.  All processing happens locally in your browser.

All tools

65 free tools that run entirely in your browser.

JSON & Data

JSON Formatter

Beautify and pretty-print JSON with a live tree view and error detection.

JSON Minifier

Compress JSON into a single line and see exactly how many bytes you saved.

JSON Validator

Validate JSON syntax and jump straight to the line and column of any error.

JSON to CSV

Convert a JSON array of objects into clean CSV, ready for Excel or Sheets.

CSV to JSON

Turn CSV rows into a JSON array of objects with header detection.

JSON to YAML

Convert JSON to readable YAML for configs, CI files and manifests.

YAML to JSON

Parse YAML into JSON and validate your config in one step.

JSON to XML

Convert JSON objects into well-formed, indented XML.

XML to JSON

Parse XML into a clean JSON structure you can work with.

JSON to TypeScript

Generate TypeScript interfaces from any JSON payload instantly.

JSON Diff

Compare two JSON documents and highlight every added, removed or changed value.

Converters

Number Base Converter

Convert numbers between binary, octal, decimal and hexadecimal.

Color Converter

Convert colors between HEX, RGB, HSL and HSV with a live preview.

CSV to Markdown Table

Paste CSV and get a GitHub-flavored Markdown table you can drop into any README.

Markdown to HTML

Render Markdown to clean, sanitized HTML with a live preview.

HTML to Markdown

Convert HTML into tidy Markdown for docs, notes and issues.

Roman Numeral Converter

Convert numbers to Roman numerals and back, up to 3,999,999.

Text to Binary

Convert text to binary, hex, octal or decimal — and decode it back.

Encode & Decode

Base64 Encode / Decode

Encode text to Base64 and decode it back, with full Unicode support.

Base64 to Image

Preview and download an image from a Base64 or data-URI string.

Image to Base64

Turn any image into a Base64 data URI for CSS, HTML or JSON.

URL Encode / Decode

Percent-encode and decode URLs and query-string components safely.

HTML Entity Encoder

Encode and decode HTML entities to escape or unescape markup.

JWT Decoder

Decode a JSON Web Token to inspect its header, payload and expiry.

URL Parser

Break a URL into protocol, host, path, query params and hash.

Backslash Escape / Unescape

Escape and unescape strings for JSON, JavaScript and other languages.

Format & Minify

SQL Formatter

Format and beautify SQL queries across MySQL, Postgres and more dialects.

XML Formatter

Pretty-print and indent XML, or collapse it back into one line.

HTML Beautifier

Format and indent messy HTML into clean, readable markup.

CSS Beautifier

Beautify and indent CSS with consistent spacing and formatting.

JavaScript Formatter

Format and beautify JavaScript with proper indentation and spacing.

CSS Minifier

Minify CSS by stripping comments and whitespace to shrink your stylesheet.

JavaScript Minifier

Minify JavaScript with a real Terser engine to reduce bundle size.

HTML Minifier

Compress HTML by removing comments and collapsing whitespace.

Text Tools

Text Diff Checker

Compare two blocks of text and highlight every difference line by line.

Case Converter

Convert text between camelCase, snake_case, kebab-case, Title Case and more.

Word & Character Counter

Count words, characters, sentences, lines and reading time as you type.

Slug Generator

Turn any title into a clean, URL-safe slug for pages and posts.

Remove Duplicate Lines

Strip duplicate lines from a list, with optional sorting and trimming.

Sort Text Lines

Sort lines alphabetically, numerically or reverse — case-sensitive or not.

Find and Replace

Find and replace text with plain-text or full regular-expression support.

Reverse Text

Reverse a string by characters, words or whole lines.

Markdown Viewer

Open and view any .md file as a clean, rendered document — drag, drop, read.

Markdown Editor & Preview

Write Markdown with a live, side-by-side rendered preview.

Remove Line Breaks

Remove or collapse line breaks and extra whitespace from text.

Generators

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.

Random Number Generator

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

NanoID Generator

Generate compact, URL-friendly NanoIDs with a custom size and alphabet.

Gitignore Generator

Build a .gitignore from templates for Node, Python, macOS and more.

Web & Design

Box Shadow Generator

Design CSS box-shadows visually and copy the exact code.

CSS Gradient Generator

Build linear and radial CSS gradients with a live preview.

Color Picker & Palette

Pick a color, get every format, and generate tints, shades and palettes.

Color Contrast Checker

Check text/background contrast against WCAG AA and AAA standards.

Meta Tag Generator

Generate SEO, Open Graph and Twitter meta tags from a simple form.

Time & Date

Unix Timestamp Converter

Convert Unix timestamps to human dates and back, in any time zone.

Cron Expression Parser

Explain a cron expression in plain English and preview its next runs.

Cron Expression Generator

Build a cron schedule with simple controls and copy the expression.

Dev Utilities

Regex Tester

Test regular expressions against text with live match highlighting.

Hash Generator

Generate MD5, SHA-1, SHA-256 and SHA-512 hashes from any text.

Bcrypt Generator

Hash a password with bcrypt and verify a value against a hash.

HTTP Status Codes

A searchable reference of every HTTP status code and what it means.

JSON Path Finder

Explore a JSON tree and copy the exact path to any value.