How to Decode a Base64 String
Decoding Base64 reverses the encoding process: each group of four Base64 characters is converted back into three bytes of original data. Simply paste your Base64 string above and click Decode from Base64 - the tool reads the characters, maps them back to their 6-bit values, reassembles the original bytes, and renders the result as UTF-8 text.
This is useful for inspecting API responses, reading JWT payloads, debugging email headers, viewing encoded configuration values, or simply checking what a mysterious string of letters and numbers actually says.
Fixing Common Base64 Decoding Errors
"Invalid character" errors
The standard Base64 alphabet only contains A-Z, a-z,
0-9, +, /, and the padding character
=. If your string contains - or _, it's likely
Base64URL - check the "URL-safe Base64" option above to decode it
correctly, or use our dedicated Base64URL tool.
Missing padding
Standard Base64 strings should have a length that is a multiple of 4, padded with
= characters if necessary. Many systems (especially JWTs and URL
parameters) strip this padding. This tool automatically restores missing padding
before decoding, so you usually don't need to fix it manually.
Garbled or unreadable output
If the decoded result looks like random characters, the original data probably wasn't text at all - it might be a binary file (image, PDF, ZIP archive, etc.). In that case, try our Base64 to Image or Base64 to PDF Base64 to File converters instead.
Frequently Asked Questions
Paste the Base64 string into the input box above and click "Decode from Base64". The decoded text appears instantly in the output box, ready to copy with one click.
This usually means the input contains characters outside the standard Base64 alphabet - often spaces, line breaks, or the URL-safe characters - and _. Enable "URL-safe Base64" above if your string came from a URL, cookie, or JWT.
If your Base64 string is missing its trailing = characters (common with Base64URL and JWTs), this tool automatically detects and restores the correct padding before decoding.
Yes. This decoder is UTF-8 aware, so Base64 strings representing emoji, Turkish, Arabic, Chinese, or any other Unicode text decode correctly and display as readable characters.
Yes. Decoding happens entirely in your browser's memory via JavaScript. The decoded output is never executed, uploaded, or stored - it's just displayed as text.
Related Tools
Base64 Encode
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Base64URL Encode/Decode
URL-safe Base64 for JWTs and tokens.
Base64 to Image
Preview and download images from Base64.
Base64 to PDF
Convert and preview Base64 PDF files.
Base64 to File
Decode Base64 back to any file type.
JSON to Base64
Encode or decode JSON payloads.
URL Encode/Decode
Percent-encode or decode URLs and text.