Base64 Decoder
Decode Base64 to text and files instantly. Decode data URIs, email attachments, and Base64-encoded data. Supports URL-safe Base64 decoding and automatic file type detection. Perfect for developers working with data URIs, API responses, and embedded content.
- Input
- Base64
- Output
- Text & Files
- Time
- Instant
- Price
- Free
Image Preview
Automatically detect and preview images from Base64 data URIs. View decoded images directly in the browser.
File Download
Download decoded files (images, PDFs, documents) with correct file extensions and MIME types.
100% Private
Everything runs locally in your browser. Your Base64 data never leaves your device.
Decode Base64 to text or files online
Paste your Base64 string, configure options, and get decoded output.
Convert - and _ to + and /.
Remove data:[mime];base64,
Privacy-first
All decoding happens locally. No uploads.
What is Base64 Decoding?
Understanding how Base64 decoding converts encoded strings back to original data
Base64 decoding is the reverse process of Base64 encoding. It converts Base64-encoded strings (which use 64 ASCII characters: A-Z, a-z, 0-9, +, /) back into their original binary or text format. When decoding Base64, the tool reverses the encoding process: it takes the Base64 characters, converts them back to bytes (each 4 Base64 characters represent 3 bytes), and then decodes those bytes to text or binary data.
When you decode Base64, the tool groups Base64 characters into sets of four (representing 24 bits total), converts each 6-bit group back to its original byte value, and reassembles the bytes into the original data. If padding characters (=) are present, they indicate how many bytes were in the final group during encoding. The decoded data can be text, images, PDFs, or any binary file.
Base64 Encoded String
SGVsbG8gV29ybGQh
16 bytes (Base64-encoded)
Decoded Text
Hello World!
12 bytes (original text)
How Base64 Decoding Works
The decoding process reverses Base64 encoding: it groups Base64 characters into sets of four (representing 24 bits total), converts each 6-bit group back to its original byte value, and reassembles the bytes into the original data. For text data, bytes are decoded using UTF-8 encoding. For binary data (images, PDFs, etc.), bytes are preserved as-is for file download.
URL-Safe Base64 Decoding
URL-safe Base64 uses - and _ instead of + and / to avoid URL encoding issues. When decoding URL-safe Base64, these characters must be converted back to + and / before standard Base64 decoding. This tool automatically detects and handles URL-safe Base64 encoding, making it easy to decode tokens, API responses, and other URL-safe Base64 strings.
Base64 Decoding is Reversible
Base64 encoding and decoding are perfect inverses. Any data encoded to Base64 can be decoded back to its original form without loss. This makes Base64 ideal for transmitting binary data as text, but remember: Base64 is encoding, not encryption—anyone can decode it.
Why Decode Base64?
Common use cases where Base64 decoding reveals original data
Image Data URIs
Decode Base64-encoded images from data URIs in HTML or CSS. Extract and view images that were embedded inline, or download them as separate image files.
Email Attachments
Decode Base64-encoded email attachments. Email systems encode binary attachments in Base64, requiring decoding to access the original files.
API Responses
Decode Base64-encoded data from API responses. Some APIs encode binary data or text in Base64 for transmission, requiring decoding to access the actual content.
URL Parameters
Decode Base64-encoded data passed through URL query parameters. Extract and view data that was encoded for safe URL transmission.
Database Storage
Decode Base64-encoded data stored in text database columns. Some databases store binary data as Base64 strings, requiring decoding to access the original files.
File Recovery
Recover files from Base64-encoded strings. Decode images, PDFs, documents, or any binary file that was encoded to Base64 for transmission or storage.
Frequently Asked Questions
Everything you need to know about Base64 decoding
How do I decode Base64?
Paste your Base64 string into the input field, enable auto-detection options if needed, and click Decode. The tool will decode the Base64 string to text or binary data that you can view, copy, or download.
What is Base64 decoding?
Base64 decoding converts Base64-encoded strings back to their original format (text, images, files, or binary data). The process reverses Base64 encoding, converting ASCII characters back to bytes and then to the original data.
Can I decode images from Base64?
Yes. If your Base64 string contains image data (from a data URI or image encoding), the tool will detect it and allow you to preview or download the image. The tool automatically detects image MIME types from data URI prefixes.
Does this tool handle URL-safe Base64?
Yes. The tool can auto-detect URL-safe Base64 encoding (which uses - and _ instead of + and /). Enable the auto-detect option to automatically convert URL-safe Base64 to standard Base64 before decoding.
What if the decoded data is binary?
If the Base64 string contains binary data (images, PDFs, etc.), the tool will detect it and allow you to download it as a file. For images, you can preview them directly in the browser. The tool automatically detects the file type from data URI prefixes.
Is my Base64 data stored on your servers?
No. All decoding happens locally in your browser using JavaScript. Your Base64 data never leaves your device and is not uploaded to any server.
How do I handle data URI prefixes?
If your Base64 string starts with 'data:[mime];base64,', enable the auto-remove prefix option. The tool will automatically strip the prefix before decoding and detect the MIME type for proper file handling.
Why is my Base64 string invalid?
Base64 strings must only contain A-Z, a-z, 0-9, +, /, and = characters (or - and _ for URL-safe). Invalid characters, incorrect padding, or truncated strings will cause decoding errors.
Can I decode any file type?
Yes. Base64 can encode any file type, and this tool can decode any Base64-encoded data back to its original format: images, PDFs, documents, text files, binary files, and more.
What's the difference between Base64 decoding and decryption?
Base64 decoding is a reversible encoding process—anyone can decode Base64 instantly. Decryption requires a secret key and is used for security. Base64 is encoding, not encryption. Never use Base64 alone for security.
Does this tool support Unicode characters?
Yes. This tool uses UTF-8 decoding after Base64 decoding, correctly handling emoji, accented characters, Chinese/Japanese text, and all Unicode symbols in decoded text.
Can I use this for production applications?
This tool is perfect for testing, debugging, and one-off decoding. For production apps with high volume, integrate Base64 decoding directly into your codebase using native libraries (Buffer in Node.js, atob in browsers, base64 module in Python) for better performance.
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