MP4 to Base64 — Video to Base64 Converter

Exactly 33.3% bigger, because three bytes become four characters. A 5 MiB MP4 produces 6,990,508 Base64 characters, plus the 22-character data:video/mp4;base64, prefix.

25 MiB. The original bytes and the ~34 MB text output both have to sit in memory at once, and a JavaScript string is capped near 512 MiB in V8, so larger files risk crashing the tab.

Only for very small clips. Inlined video cannot be range-requested, streamed or cached separately, and it inflates the HTML or CSS file by a third. Serve anything longer than a couple of seconds as a normal file over HTTP.

That is RFC 4648 padding. When the file length is not a multiple of three, the last group is short and is padded with one '=' (length ≡ 2 mod 3) or two '=' (length ≡ 1 mod 3) so the output stays a multiple of four characters.

Yes — four containers are accepted: MP4 (including .m4v), WebM, QuickTime .mov and Ogg .ogv. The MIME type of whichever file you pick is written into the data URL prefix, so a WebM comes back as data:video/webm;base64, and still plays in the built-in preview.

No. The file is read straight from your device with the browser's own file API and encoded in the page, so the bytes never leave your machine — there is no server, no account and no upload step, which is the point of doing it in the browser.

Copy data URL puts the whole string on your clipboard, and Download .txt saves it next to your file name as <name>.base64.txt. The panel only prints the first 400 characters on screen, because rendering several million characters would lock up the tab.

The tool feeds the generated data URL straight back into a video element below the result, so if the preview plays, the string is valid and complete. If it does not play, the browser cannot decode that codec, which is a codec problem rather than a Base64 one.