Base64 DecoderDecode Base64 Strings to Text, Images & Files
The fastest Base64 decoder on the web — paste any Base64 string and decode it to readable text, preview images live, detect file types automatically. Works offline, 100% private.
Paste Base64 to see the decoded result
Everything You Need to Decode Base64
From instant decoding to image previews — every feature for working with Base64-encoded data.
Instant Base64 Decoding
Paste any Base64 string and get the original text, image, or file data back instantly. Handles all standard Base64 formats including MIME, PEM, and data URIs.
Live Image Preview
When you decode Base64-encoded images (JPEG, PNG, GIF, WebP), see a live visual preview right in the output panel. Verify decoded images at a glance.
Auto Decode While Typing
Results update live as you type with smart debouncing. Toggle Auto Decode off for manual mode when working with very large Base64 strings.
Smart MIME Type Detection
Auto-detects file types from Base64 headers (magic bytes). Knows if it's a JPEG, PNG, GIF, WebP, PDF, ZIP, or plain text — no guessing needed.
Comprehensive Validation
Real-time Base64 format validation checks character set, string length, and padding correctness. Clear error messages tell you exactly what's wrong.
File Upload & Drag & Drop
Upload .b64, .base64, .pem, .cer, .crt files or any text file containing Base64. Drag and drop works directly on the input area.
Undo & Redo History
Full undo/redo with keyboard shortcuts (Ctrl+Z, Ctrl+Y). Every decoding step is tracked — experiment freely and revert anytime.
Copy, Download & Share
Copy decoded output to clipboard, download as .txt file, save decoded images directly, or generate a shareable link.
Works Completely Offline
All decoding runs locally in your browser using built-in JavaScript APIs. No server requests, no latency, no data ever leaves your device.
How Base64 Decoding Works
Paste Base64 String
Copy any Base64-encoded string — from email attachments, JSON payloads, data URIs, API responses, or PEM certificates — and paste it into the input panel.
Auto Decode or Manual
By default, decoding happens instantly as you type with validation feedback. Toggle Auto Decode off for manual control with large inputs.
Review Output & Preview
See the decoded text, or for images — a live visual preview with the detected MIME type. Validation indicators show you if the Base64 format is correct.
Copy, Download, or Share
Copy decoded text to clipboard, download as .txt, save decoded images, or share via link. Everything stays private — your data never leaves the browser.
Better Than Other Base64 Decoders
100% Private & Secure
Unlike server-side Base64 decoders that can see your data, everything runs in your browser. Your Base64 strings and decoded content never leave your device.
Instant, No Waiting
Browser-native atob() handles decoding at native speed. Zero network latency, no server queues — results appear as fast as you can paste.
Image Preview Built-In
When your Base64 contains an image, you see it instantly. JPEG, PNG, GIF, WebP — all render live in the output panel with MIME type labels.
Smart Format Detection
Magic byte analysis tells you the file type before decoding. PDFs, ZIPs, images — each is identified from the Base64 header so you know exactly what you're decoding.
Clear Error Messages
Invalid Base64? Wrong padding? Bad characters? Each error is caught and explained in plain English. Fix issues fast without guessing what went wrong.
Enterprise-Ready Security
Decode PEM certificates, API tokens, and authentication data safely. Zero data transmission means zero risk of exposure — ideal for security-sensitive environments.
Everything About Base64 Decoding
Base64 decoding converts Base64-encoded strings back to their original binary or text form. You need it when working with Base64-encoded data from email attachments (MIME), JSON API payloads, HTML data URIs (embedded images), PEM certificates, JWT tokens, or any system that transmits binary data as text. Our decoder handles all these formats — just paste and get the original content back immediately.
Our decoder uses the browser's built-in atob() function for decoding, with full Unicode support via the decodeURIComponent/escape wrapper. When you paste a Base64 string, the tool validates the format (character set, length, padding), detects the MIME type from magic bytes (/9j/ for JPEG, iVBOR for PNG, etc.), and decodes the content. For images, a live preview is shown. Everything runs locally in your browser — no server involved.
Yes! That's one of the standout features. When you paste a Base64-encoded JPEG, PNG, GIF, or WebP, the tool detects the image type from the Base64 header and renders a live preview right in the output panel. You can download the decoded image directly as a file. If the Base64 is from a data URI (starting with data:image/...), just paste the Base64 portion after the comma.
You can decode any valid Base64 string regardless of content type. Common use cases include: text and code, images (JPEG, PNG, GIF, WebP), PDF documents, ZIP archives, PEM certificates (.pem, .cer, .crt), JWT tokens (the payload portion), email attachments (MIME), and data URIs. The tool auto-detects the MIME type and shows image previews when applicable. For binary formats like PDFs, the decoded output shows as raw text.
The tool validates Base64 in real-time across three checks: character set (only A-Z, a-z, 0-9, +, /, and = padding allowed), string length (must be a multiple of 4), and padding correctness (the = padding must match the encoded content). Invalid input is flagged immediately with a clear error message explaining what's wrong. The input panel gets a red border when errors are detected, and goes back to normal when fixed.
Absolutely. 100%. All decoding happens entirely in your browser using client-side JavaScript. Your Base64 strings — including any containing sensitive data like API keys, authentication tokens, PEM private keys, or personal documents — are never uploaded, transmitted, stored, or logged on any server. We have no way of seeing your data. The optional auto-save stores data in your browser's localStorage only. Safe for enterprise and personal use.
Yes. Once the page loads in your browser, you can disconnect from the internet and continue using all features — decode Base64, view image previews, undo/redo, copy, download, share. Every operation runs locally with zero network requests after the initial page load. Perfect for secure environments, air-gapped systems, or working on planes.
Yes. Our decoder uses the standard decodeURIComponent/escape wrapper around atob() to properly handle multi-byte UTF-8 sequences. When your Base64 encodes international text (Arabic, Chinese, Cyrillic, Japanese, emoji, etc.), it decodes correctly without corruption. This follows the recommended approach in MDN Web Docs and ensures your international text is restored perfectly.
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