Base64 Encoder / Decoder
Encode text or files to Base64 and decode Base64 back to text or a file, in standard or URL-safe Base64URL, right in your browser.
Base64 Encoder / Decoder
Type or paste text. It is encoded as UTF-8 as you go.
Sizes
- Input
- –
- Output
- –
Quick facts
- Price
- Free
- Sign-up
- Not required
- Where it runs
- On your device
- Files uploaded
- No
- Limits
- Up to 5 MB per input; Up to 1 file at once
- Updated
Base64 Encoder / Decoder turns text or a file into Base64, and turns Base64 back into text or a downloadable file. It is for developers who meet Base64 in API payloads, email sources, data: URLs, JSON Web Tokens and configuration files, and need to read or produce it quickly. It handles both alphabets, standard Base64 and the URL-safe Base64URL, and when a string will not decode it names the character that breaks it and where that character sits.
How to use
- Choose Encode or Decode at the top. Each mode keeps its own input, so you can switch back and forth without losing what you typed.
- To encode, pick the alphabet: standard Base64 with
+,/and=padding, or Base64URL with-,_and no padding. Then type or paste text, or drop one file on the drop zone (or click it to browse). - To decode, paste the Base64 string. The alphabet is detected for you, and a
data:URL is read from after its comma. - Read the result as it updates. Press Copy result to put it on your clipboard. When the decoded bytes are not text, the tool says what kind of file they look like and offers a Download button instead; decoded text can be saved as a .txt file too.
- Press Clear to empty the current mode.
Examples
Encoding the text Hello, world! with the standard alphabet gives:
SGVsbG8sIHdvcmxkIQ==The two = signs are padding: 13 bytes do not fill the last group of three, so the output is rounded up to a multiple of four characters. With Base64URL the same text gives SGVsbG8sIHdvcmxkIQ, with the padding left out.
Text that is not plain English is encoded as UTF-8 first, so café becomes Y2Fmw6k=: the letter é takes two bytes. The two bytes 0xFB 0xFF show how the alphabets differ: standard Base64 writes them as +/8=, Base64URL as -_8, and the decoder reads either form.
Limits
Input and output are capped at 5 MB, one file at a time. A decode that is not valid UTF-8 text, or that holds control characters other than tabs and line breaks, is offered as a download rather than shown. The file type is a guess from the first bytes and covers common formats only; anything else is saved as a .bin file. Base64 is about a third larger than the data it encodes, so a 5 MB file gives close to 7 MB of text.
FAQ
Is my text or file uploaded anywhere?
No. The encoding and decoding run in the page itself, in the memory of your browser. A file you drop is read locally, and the download is created from that same memory, so nothing is sent to a server.
What is the difference between Base64 and Base64URL?
They share 62 characters and differ in two. Standard Base64 uses plus and slash, which have special meanings inside web addresses; Base64URL replaces them with minus and underscore so the string can sit in a URL, a cookie or a file name unchanged. JSON Web Tokens use Base64URL without padding.
Why does decoding say the Base64 is cut short or the padding is wrong?
A Base64 string is built from groups of four characters. A last group of a single character cannot hold a whole byte, which usually means a character was lost when the string was copied. Padding must bring the length to a multiple of four, so check that nothing was trimmed from either end.
Is Base64 a kind of encryption?
No. Base64 only changes how bytes are written, and anyone can reverse it without a key. Never use it to hide a password or a secret; use it to carry binary data through places that accept only text.