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Binary, hex, Roman numerals, Base64, URL encoding and passwords, all in your browser.
Browse all calculatorsEncode text or files to Base64 and decode them back, with emoji, URL-safe and MIME options. Nothing leaves your browser.
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Paste Base64 or a data URI to see the file type and size.
Private by design. Everything runs in your browser and is never uploaded.
Base64 is a way to write any data using only 64 printable characters: A to Z, a to z, 0 to 9, plus and slash. Every 3 bytes become 4 characters, so the result is about a third longer. It lets binary data travel through text-only channels. It is an encoding, not encryption, so anyone can decode it.
This tool encodes and decodes in both directions. Text is turned into UTF-8 bytes first, so accents, emoji and non-Latin scripts survive a round trip. To see the 0s and 1s underneath, try the binary translator.
| Text | Bytes in hex | Base64 |
|---|---|---|
| (empty) | (none) | (empty) |
| f | 66 | Zg== |
| fo | 666F | Zm8= |
| foo | 666F6F | Zm9v |
| foob | 666F6F62 | Zm9vYg== |
| fooba | 666F6F6261 | Zm9vYmE= |
| foobar | 666F6F626172 | Zm9vYmFy |
| é | C3A9 | w6k= |
| 😀 | F09F9880 | 8J+YgA== |
Four steps, and the result updates as you type.
Choose Text or File, then Encode or Decode. In the File tab, Encode reads a file from your device and Decode rebuilds a file from Base64.
Use the standard alphabet or the URL-safe one, keep or remove the = padding, and wrap lines at 76 characters when the Base64 is for email.
Text converts live as you type. Spaces and line breaks in pasted Base64 are ignored, and a bad character is named with its position.
Copy the result or save it as a .txt file. Open the working to see how the first bytes are regrouped from 8 bits to 6 bits.
Everything the converter does comes down to these three tables.
| Index | Standard alphabet | URL-safe alphabet |
|---|---|---|
| 0 to 25 | A to Z | A to Z |
| 26 to 51 | a to z | a to z |
| 52 to 61 | 0 to 9 | 0 to 9 |
| 62 | + | – |
| 63 | / | _ |
| Padding | = | = (often left off) |
| Bytes in the last group | Characters written | Padding | Example |
|---|---|---|---|
| 3 | 4 | none | foo gives Zm9v |
| 2 | 3 | one = | fo gives Zm8= |
| 1 | 2 | two = | f gives Zg== |
| Original size | Bytes | Base64 characters | Longer by |
|---|---|---|---|
| 1 KB | 1,024 | 1,368 | +33.6% |
| 10 KB | 10,240 | 13,656 | +33.4% |
| 100 KB | 102,400 | 136,536 | +33.3% |
| 1 MB | 1,048,576 | 1,398,104 | +33.3% |
| 10 MB | 10,485,760 | 13,981,016 | +33.3% |
Four standards use the same idea with small differences, so pick the one the receiving system expects.
| Variant | Characters 62 and 63 | Padding | Line breaks | Defined in |
|---|---|---|---|---|
| Standard Base64 | + and / | = | None added | RFC 4648, section 4 |
| URL and filename safe | – and _ | = (may be omitted) | None added | RFC 4648, section 5 |
| MIME (email) | + and / | = | Lines of at most 76 characters | RFC 2045, section 6.8 |
| Data URI | + and / | = | None | RFC 2397 |
| Feature | This tool | Typical online converter |
|---|---|---|
| Encode and decode | One page, same options | Often a separate page for each direction |
| URL-safe alphabet and optional padding | Both, live | Not on every converter |
| 76-character MIME wrapping | With LF or CRLF line endings | Offered by some, missing on others |
| Errors | Names the bad character with line and column | Often a generic message or none |
| Decoded images | Preview before you download | Often a direct download with no preview |
| Working shown | First bytes as 8-bit and 6-bit groups | Rarely |
| Where files are processed | In your browser only | Some tools process files on a server |
Turn an icon or logo into a data URI and paste it straight into HTML or CSS. RFC 2397 says the scheme is only useful for short values, so keep it for small files.
Paste a string from a config file, an API response or a log and read what it says. If the text is a long document, copy it into the online notepad to keep working on it.
MIME email wraps Base64 at 76 characters per line. Switch Line wrap to 76 with CRLF and the output follows that rule.
Choose the URL-safe alphabet and remove the padding to get a string that fits in a URL or file name without escaping.
Encode a phrase, decode it again and check that every character survived. To spot a changed character fast, run the two versions through the text compare tool.
Paste the Base64 of a PDF, image or archive into the File tab, check the detected type and download it with the right extension.
A few details explain most surprises. If a copied value arrives with hidden formatting, clean it first with the remove text formatting tool, or decode a binary dump with the binary to text converter.
RFC 4648 says base encoding provides no computational confidentiality. To protect a secret, use real encryption or a strong value from the random password generator.
Four characters carry three bytes, so Base64 is roughly a third larger than the original, plus a little for padding and line breaks.
The = signs fill the last group of 4. RFC 4648 allows leaving them off when the length is known, so this tool accepts input without them.
The browser function btoa throws an error for characters above U+00FF. This tool converts text to UTF-8 bytes first, so any character works.
Spaces and line breaks are skipped when decoding, as MIME does. Any other stray character is reported instead of silently dropped.
Reading, encoding, decoding and previewing all happen in your browser. Nothing you type or choose is sent to a server.
Files and decoded data are capped at 10 MB. The text boxes take up to 1,000,000 characters, and the result box shows the first 20,000 characters while Copy and Download include everything.
Text can be read and written as UTF-8, ISO-8859-1, UTF-16 LE or UTF-16 BE. Other legacy code pages are not included, and UTF-8 is the right choice for most data. See RFC 4648 for the encoding itself.
The tool gives you the bytes back and names the file type. It does not decrypt, unzip, verify signatures or open the contents of a token. Data URIs follow RFC 2397.
The alphabets, padding and line-length rules on this page come from these references.
Short answers to what people ask most.
Base64 writes binary data as text using 64 printable characters: A to Z, a to z, 0 to 9, plus and slash. Every 3 bytes become 4 characters, so the result is about a third longer. It is defined in RFC 4648.
Choose Decode, then paste the Base64 into the box and the text appears as you type. Spaces, line breaks and a missing = padding are accepted, and any other invalid character is named with its position.
No. Base64 is a reversible encoding with no key, and RFC 4648 notes that it provides no computational confidentiality. Anyone can decode it, so do not use it to hide passwords or private data.
Base64 works in groups of 3 bytes. When the last group has 2 bytes the output ends with one =, and when it has 1 byte it ends with two ==, so the length is a multiple of 4.
Four characters carry three bytes, so the output is about 33 percent longer. Padding and optional line breaks add a little more.
URL-safe Base64 replaces + with – and / with _ so the result can sit in a URL or file name without escaping. It is defined in section 5 of RFC 4648, and the = padding is often left off.
The most likely cause is the wrong text encoding. This tool reads the decoded bytes as UTF-8 by default, so if the source used UTF-16 or Latin-1, change the Text encoding option. If the bytes are not text at all, the tool says so and offers to open them as a file.
Open the File tab, choose Encode, then drop your file or pick it from your device, up to 10 MB. Choose Plain Base64 or Data URI, then copy the result or download it as a .txt file.
Open the File tab, choose Decode and paste the Base64 or a full data URI. The tool detects the file type, previews images, lets you set the file name and downloads the file.
The input contains a character outside the Base64 alphabet, such as a stray punctuation mark, a smart quote or an accidental letter. The message gives the position, line and column so you can fix it. Spaces and line breaks are ignored.
MIME email, defined in RFC 2045, limits encoded lines to 76 characters. Turn on Line wrap to break the output at 76 characters, with LF or CRLF line endings.
No. Encoding, decoding and file reading all run in your browser, and nothing you type or choose is sent to a server. Your alphabet, padding, wrap and text encoding choices are saved on your own device only.