UtilTools

Base64 Encoder / Decoder

Encode and decode Base64, including UTF-8 and URL-safe.

Base64 Encoder / Decoder converts text and files to and from Base64, handling UTF-8 correctly — which the naive btoa call does not — and supporting the URL-safe alphabet used in JWTs and query strings. Everything is computed locally, so tokens and credentials are not exposed.

Loading Base64 Encoder / Decoder…

Runs entirely on your device. No file or text you enter here is uploaded. How to verify it.

How to use Base64 Encoder / Decoder

  1. Paste text or Base64, or drop a file.
  2. Choose standard or URL-safe alphabet.
  3. Copy the converted output.

Questions about Base64 Encoder / Decoder

Why does plain btoa fail on non-ASCII text?
Because btoa expects a byte string and throws on any code point above 255. Text has to be encoded to UTF-8 bytes first. This tool uses TextEncoder, so emoji and accented characters round-trip correctly.
What is URL-safe Base64?
The same encoding with + and / replaced by - and _, and padding usually dropped, so the result survives being put in a URL or a filename. It is what JWT segments use.
Is Base64 encryption?
No, and this matters. It is an encoding — completely reversible by anyone, with no key. Base64 hides nothing. For actual secrecy use Text Encryption.
How much bigger does Base64 make a file?
About a third bigger: every three bytes become four characters, plus padding. A 3 MB image comes out as roughly 4 MB of text, which is why inlining large assets as data URIs usually costs more bandwidth than it saves.
Is there a size limit on the file I can encode?
The limit is browser memory, since the encoded result is held as one string. A few hundred megabytes is usually workable on a desktop; on a phone expect trouble well before that.
Is Base64 Encoder / Decoder really free, with no limits?
Yes. There is no account, no daily cap, no file-size tier and no watermark, because there is no server cost to recover. The site is funded by clearly disclosed partner recommendations on the Partners page, never by metering the tools.
Are my files or text uploaded when I use Base64 Encoder / Decoder?
No. Everything is processed by JavaScript running in your browser, on your device. You can verify it: open your browser's developer tools, switch to the Network tab, and use the tool. You will see no request carrying your data — because there is nowhere for it to go.