Base64 Converter Pro

A professional, fully client-side Base64 tool. No server. No uploads. Works offline after first load.

Live demo on GitHub Pages

Features

Encoding

• Base64 (Standard), Base64 URL-Safe, Base32, Base58 (Bitcoin), Hexadecimal, ASCII85
• Drag-and-drop files or entire folders — batch encode to ZIP
• Paste images directly from clipboard (Ctrl+V)
• Fetch a URL and encode it on the spot
• Gzip compression before encoding (skips already-compressed formats)
• Image resize before encode (custom width × height)
• Line-wrap output (76-char MIME / PEM / no-wrap)
• Split output into chunks for size-limited APIs
• Auto-format detection on paste (Hex / Base32 / Base58 / Base64URL / Base64 / ASCII85)

Decoding

• Paste any Base64 string — with or without data:mime;base64, prefix
• Auto-detect MIME type from magic bytes
• Auto-detect encoding format on input
• Preview decoded images, video, and audio inline
• Download decoded file with correct extension
• PEM wrap/unwrap — generate -----BEGIN CERTIFICATE----- blocks from raw Base64

Text

• Live encode/decode as you type (200 ms debounce)
• Ctrl+Enter to encode/decode
• Swap input ↔ output
• Supports all encoding formats

JWT Decoder

• Paste any JWT — header, payload, and signature decoded instantly
• Human-readable timestamps for exp, iat, nbf
• Expiry status (Valid / EXPIRED) highlighted
• Algorithm and subject shown in info bar
• Live decode as you type

Code Generation

Outputs ready-to-paste snippets in: HTML, CSS, JavaScript, TypeScript, Python, C#, PowerShell, Go, Rust, Bash, PHP, Ruby, Kotlin, JSON, curl, wget

Other

• QR code from any encoded string
• MD5 / SHA-1 / SHA-256 hashes of original file
• Compare two Base64 strings (diff / similarity)
• Deep links — ?data=...&mode=decode|text|jwt&format=base64
• Copy shareable link — pre-populated decode links
• Font-size slider — adjust output font (11–20px, saved to localStorage)
• Session stats (files, bytes, speed, ratio)
• History with localStorage (last 50 conversions)
• Dark / light theme toggle
• Offline PWA — install to desktop/home screen
• Format detection badge — auto-detect encoding on paste

Usage

Open index.html in any modern browser — no build step, no server needed.

# Clone and open
git clone https://github.com/SysAdminDoc/Base64Converter.git
cd Base64Converter
start index.html     # Windows
open index.html      # macOS
xdg-open index.html  # Linux

Or use the hosted version: https://sysadmindoc.github.io/Base64Converter/

Deep Links

# Pre-load a value into the Decode tab
?data=SGVsbG8gV29ybGQ=&mode=decode

# Pre-load into Text tab with URL-safe format
?data=dGVzdA&mode=text&format=base64url

# Decode a JWT directly
?data=eyJhbGciOiJIUzI1NiJ9...&mode=jwt

Architecture

Single index.html with all CSS and JS inlined. No build toolchain required.

• Web Worker — encoding runs off the main thread to prevent UI lockup
• fflate (CDN) — gzip compression
• qrcode.js (CDN) — QR code generation
• SubtleCrypto — SHA-1 / SHA-256 hashing
• Service Worker (sw.js) — cache-first offline support

License

MIT