BMP to Base64 Converter

What is BMP (and why it still shows up)

BMP (Bitmap) is a long-lived Windows image format. It is simple and widely supported in legacy toolchains, which is exactly why it refuses to die: scanner exports, fax middleware, ERP attachments, older design assets, and some industrial UIs still emit .bmp files.

Those pipelines often need the image as text next — an API field, a unit-test fixture, a CSS sprite experiment, or a single-file HTML demo. Base64 is the bridge: the bytes become ASCII you can paste anywhere binary uploads are awkward. You are not required to convert BMP to PNG first just to encode it.

How to convert a BMP to Base64

1. Pick the file. Drag a .bmp onto the drop zone, or use the site-wide Image to Base64 tool.
2. Choose the output shape. The same encode supports four paste targets (see next section).
3. Copy once, paste once. Long strings break when messengers insert line wraps.

Prefer a modern format for web delivery? Encode PNG or JPG instead via PNG to Base64 or JPG to Base64.

Raw Base64 vs data URI — which shape to copy

For API-oriented payloads, see Image to Base64 for API.

JavaScript snippet (FileReader)

If you are wiring this into your own page, the browser API is enough — no WASM decoder required for encoding:

<input type="file" id="bmp" accept=".bmp,image/bmp,image/x-ms-bmp">
<pre id="out"></pre>
<script>
document.getElementById('bmp').addEventListener('change', (e) => {
  const file = e.target.files && e.target.files[0];
  if (!file) return;
  const reader = new FileReader();
  reader.onload = () => {
    const dataUrl = reader.result; // data:image/bmp;base64,...
    const raw = String(dataUrl).split(',')[1] || '';
    document.getElementById('out').textContent =
      'DATA URI:\n' + dataUrl.slice(0, 80) + '...\n\nRAW:\n' + raw.slice(0, 80) + '...';
  };
  reader.readAsDataURL(file);
});
</script>

Size notes for BMP embeds

Uncompressed BMP is often much larger than the same picture as PNG or JPEG. Base64 then adds ~33%. Check size with the Base64 image size calculator. Prefer converting large bitmaps to PNG/JPEG first when the consumer accepts those formats. Keep BMP→Base64 for small icons, fixtures, and true legacy hand-offs. See also TIFF to Base64 and HEIC to Base64.

Troubleshooting

Preview works, paste fails in the app. You likely pasted a truncated string or the wrong shape (raw vs data URI).

MIME type looks wrong. Some systems expect image/x-ms-bmp instead of image/bmp.

File is huge. That is usually the BMP, not Base64. Compress or convert before encoding.