Base64 File Decoder

Base64 File Decoder

Accepts either raw Base64 text or a data URL whose metadata ends in ;base64,. Data URLs with parameters such as data:text/plain;charset=utf-8;base64,... are recognized. Whitespace is removed before decoding; an empty input and malformed Base64 are rejected by the browser decoder.

Verified example: SGVsbG8= with output name hello.txt and MIME type text/plain creates a five-byte Blob containing Hello. The same payload works in a data URL, where the media type in the URL overrides the MIME field.

The decoded download uses the filename field, defaulting to decoded-file.bin, and the MIME field defaults to application/octet-stream. Changing a filename extension or MIME label does not convert the decoded bytes into another file format; the Base64 payload must represent the intended original file.

Whitespace-free Base64 is limited to 48 MiB of text, and raw pasted content is rejected above twice that bound to limit whitespace-heavy input. Decoding uses browser memory for the source string, binary string, byte array and Blob, so devices can run out of memory before the theoretical limit. URL-safe Base64 using - and _ is not converted automatically.

Processing and Blob creation happen locally in the current browser. A successful run enables Download result; a new run clears the previous downloadable Blob first so failed input cannot leave a stale file active. Clear removes the pasted Base64 and disables the download. Treat decoded files as untrusted content and scan or inspect them before opening.