Base64 turns arbitrary bytes into ASCII, which is why it shows up in email attachments, data URLs, HTTP headers and JSON payloads. This converter handles UTF-8 correctly, so accented letters, emoji and CJK text survive the round trip.
Input
Output
When to use URL-safe Base64
The standard alphabet uses plus and slash, which have meaning inside URLs and filenames. The URL-safe variant replaces them with minus and underscore and often drops trailing equals padding. Use it for tokens, JWT segments, cache keys and anything that will be copied into a query string; use the standard alphabet for MIME bodies and data URLs.
Base64 is not encryption
Base64 is reversible with no key, so it protects nothing. Anyone who intercepts a Base64 string can decode it in a second. It exists to make binary data safe to move through text-only channels, not to keep it secret.
Common Base64 failures
- Invalid length: a Base64 string must have a multiple of four characters after padding. Extra or missing characters produce an error.
- Missing padding: some systems strip the trailing equals signs. Decoders should add them back before decoding.
- Wrong alphabet: a string containing minus or underscore in the wrong mode will fail or decode to garbage.
- Not UTF-8: if the decoded bytes are an image or an archive, this text decoder will report invalid UTF-8. That is expected; use a binary tool for binary payloads.
Text is encoded as UTF-8 before Base64 encoding and decoded back to UTF-8 afterwards. All processing happens in this tab.