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Select Encode or Decode, then switch between UTF-8 Text and binary File mode.
Free Base64 Encoder & Decoder - Fast Browser Tool
Convert UTF-8 text and binary files using Standard Base64 or Base64url. Everything runs locally in your browser-nothing is uploaded.
100% local processing
Text and binary files
Strict validation
No external libraries
Drop a file here
or select a file to encode. Maximum input size: 20 MB.
No file selected.
Decoded file ready
Ready. Your content stays on this device.
Input characters
0
Input bytes
0 B
Output characters
0
Output bytes
0 B
Size change
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Shortcut: Ctrl/โ + Enter to convert
How it works
Encode or decode Base64 in three simple steps
Choose your workflow, provide text or a file, and download or copy the accurately converted result.
Configure the format
Use Standard Base64 or Base64url and control padding, line wrapping, whitespace, or Data URL output.
Copy or download
Copy text results instantly or download encoded text and decoded binary data without uploading anything.
Format guide
Standard Base64 compared with Base64url
| Feature | Standard Base64 | Base64url |
|---|---|---|
| Alphabet ending | + / | - _ |
| Padding | Usually uses = | Often omits = |
| Typical use | Email, APIs, files, Data URLs | URLs, filenames, JWT segments |
| Data URL support | Supported by this tool | Not used for Data URL generation |
Understanding Base64
Reliable conversion for Unicode text and binary data
Base64 is encoding-not encryption
Base64 represents arbitrary bytes using printable ASCII characters. Anyone can decode it, so it must never be treated as encryption, password protection, signing, or secure storage.
Accurate UTF-8 text handling
JavaScript's direct btoa() text usage cannot safely process many Unicode characters. This tool first converts text to UTF-8 bytes using TextEncoder. During text decoding, malformed UTF-8 is rejected instead of being silently replaced with incorrect characters.
Strict canonical validation
Decoder input is checked for the selected alphabet, legal trailing padding, valid length, and canonical unused bits. Standard and URL-safe alphabets cannot be mixed. Optional ASCII whitespace is removed only when the visible decode option is enabled.
Private binary file processing
Files are read with native browser APIs and are never rendered or executed. Decoded bytes are exposed only as a downloadable Blob. The 20 MB limit keeps memory usage predictable on desktop and mobile.
Common uses
Where Base64 is useful
API payloads
Represent small binary values in JSON, XML, or text-based protocols.
JWT inspection
Work with URL-safe encoded JWT header and payload segments.
Data URLs
Create a MIME-prefixed Standard Base64 value for compatible workflows.
Email attachments
Inspect or create encoded content used in MIME-based messages.
Developer debugging
Validate unknown Base64 strings and identify malformed input accurately.
Binary recovery
Restore valid Base64 content to a downloadable file without rendering it.
Frequently asked questions
Base64 Encoder & Decoder FAQ
Is Base64 encryption?
No. Base64 only represents binary data as text. It provides no secrecy, authentication, or password protection.
Does this tool upload my text or files?
No. Encoding and decoding happen locally in your browser. This page does not send your content to a server.
What is the difference between Standard Base64 and Base64url?
Standard Base64 uses + and /, while Base64url uses - and _ so the result is safer inside URLs, filenames, and JWT segments.
Can this tool decode Base64 without equals padding?
Yes. Valid unpadded input is normalized internally. A length remainder of one is invalid and malformed or non-canonical input is rejected.
Why can valid Base64 fail when decoded as text?
Base64 can contain any binary bytes. Text mode requires those bytes to be valid UTF-8, so arbitrary file data may only be downloaded through File mode.
Can I encode and decode binary files?
Yes. File mode reads files as bytes and can restore decoded bytes as a downloadable file, with a 20 MB safety limit.
What is a Base64 Data URL?
A Data URL combines a MIME type and Standard Base64 payload, such as data:image/png;base64, followed by the encoded data. This tool never renders decoded Data URLs; it only creates a downloadable Blob.
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