Base64 to BMP
Paste a Base64 string or a data URI and download it as a BMP image. Everything runs in your browser — nothing is uploaded.
How to convert Base64 to a BMP
Paste your data into the box above. You can give it a full data URI — a string of the form data:image/bmp;base64,Qk… — or just the raw Base64 payload without the data: prefix. The tool decodes the bytes locally and confirms it's a bitmap by reading the file's magic bytes: a real BMP begins with the two ASCII characters BM (0x42 0x4D). A live preview appears immediately. When it looks right, click Download BMP to save the file as image.bmp.
Why isn't my BMP showing?
If the preview stays empty or you get an error, one of these is usually the cause:
- The string is truncated. A partial copy cuts off the end of the image, so the bytes don't form a complete, valid file. BMP is uncompressed, so files run large and are easy to clip.
- It's URL-safe Base64 without padding. That's handled automatically — the tool converts
-and_back to+and/and re-adds the missing=padding before decoding. - The data isn't actually a BMP. A real BMP starts with
BM(0x42 0x4D). Base64 of a PNG, a PDF, or some other blob will decode into bytes, but won't carry that signature. - A copy/paste added stray characters. Line breaks and spaces are stripped automatically, but quotes, HTML entities, or a stray prefix can corrupt the payload.
Tip: BMP stores pixels uncompressed, so even a small image can be tens of thousands of Base64 characters — make sure you copied the entire string.
Decoding a data URI
You don't need to strip anything by hand. Paste the whole data URI including the data:image/bmp;base64, prefix and the tool removes it automatically before decoding. Pasting just the raw Base64 payload works too — both paths produce the same downloadable BMP.
Is this private?
Yes. The decoding happens entirely client-side in JavaScript. The Base64 you paste is decoded into bytes in the browser and turned into an object URL locally — it is never sent to a server. You can confirm this by opening DevTools → Network: pasting and decoding fires no request.
Frequently asked questions
How do I convert Base64 to a BMP?
Paste a full data URI (data:image/bmp;base64,Qk…) or just the raw Base64 payload into the box above. It decodes the bytes locally, checks the BM signature at the start of the file, shows a preview, and lets you download the result as a BMP.
Why isn't my BMP showing?
Usually the string is truncated, it isn't actually a BMP, or a copy/paste introduced stray characters. A valid BMP starts with the bytes BM (0x42 0x4D). If the bytes don't form a recognizable image, the preview will fail to load.
Can I decode a data:image/bmp;base64 URI?
Yes. Paste the whole data URI including the data:image/bmp;base64, prefix and it's stripped automatically before decoding. Pasting just the raw Base64 payload works too.
How do I convert a BMP TO Base64?
Use the BMP to Base64 tool to go the other way — drop a BMP and get a data URI you can paste into HTML or CSS.
Need to encode a BMP?
The main base64.dev tool handles text, files, and URL-safe mode with auto-detect.
Open base64.dev →