Encode or decode Base64 strings, images, and files instantly, with full UTF-8 support for text and safe handling of binary data in your browser.
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Base64 encoding transforms binary data, such as images, PDFs, or executable files, into a text-based format built from 64 printable characters (A-Z, a-z, 0-9, + and /). This lets binary content travel safely through systems and formats, like JSON, XML, or plain text emails, that were only designed to handle text.
Encoding takes 3 bytes of raw input at a time and represents them as 4 Base64 characters; decoding reverses that exact process to rebuild the original bytes. Because the two operations are perfect inverses, encoding text and then decoding the result always returns the exact original data with nothing lost.
A common misconception is that Base64 hides or protects data, but it does not. Encoding is fully reversible by anyone using a free online tool or a single line of code, so it should never be used to store or transmit passwords, API keys, or other secrets that need real confidentiality.
Every 3 bytes of input become 4 Base64 characters, so encoded text is roughly one-third larger than the original. If the input length is not a multiple of 3, one or two "=" padding characters are added at the end to keep the output length a multiple of 4.
Base64 shows up constantly in web development: embedding small images directly inside CSS or HTML as data URIs, encoding the header and payload segments of a JSON Web Token (JWT), attaching files to emails via MIME, and passing binary values through JSON-based API payloads that only support text.
The standard Base64 alphabet uses + and / as its final two characters, but both are reserved in URLs, so a URL-safe variant swaps them for - and _ instead. This tool automatically normalizes either style and restores any missing "=" padding before decoding, so pasted tokens from URLs or JWTs still convert correctly.
Encoding the text "Hello" produces the Base64 string "SGVsbG8=", where the trailing "=" is padding because 5 bytes is not a multiple of 3. Pasting "SGVsbG8=" back into decode mode returns exactly "Hello", showing that the process is lossless and fully reversible.
Quick answers about how this tool works.
Encoding (such as Base64) is a public algorithm designed to translate data formats to ensure compatibility across different systems and transport layers; it does not require a secret key and can be decoded by anyone. Encryption is a secure method designed to keep data confidential using mathematical algorithms and secret keys; it can only be decrypted by those who hold the correct decryption key.
Standard JavaScript atob() and btoa() functions only support 8-bit binary strings (Latin-1 characters). If you pass multi-byte Unicode characters (like emojis or foreign alphabets), it throws a Character Out of Range exception. This tool resolves this by converting Unicode strings to UTF-8 percent-encoded bytes before encoding, and reversing the process when decoding, ensuring safe representation of all symbols.
Base64 groups binary data into chunks of 24 bits, representing them as four 6-bit characters. If the final binary block contains only 8 or 16 bits, padding characters ("=") are appended to the end of the encoded string to ensure the total string length is a multiple of 4.
Standard Base64 uses "+" and "/" characters, which have special meanings in URLs and can cause issues. URL-safe Base64 replaces "+" with "-" and "/" with "_", and often removes the trailing "=" padding characters to prevent transmission and parsing errors.
Plain-language explainers that sit next to this tool.
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