1Upload the BMP images that came out the wrong way round.
2Pick a quarter turn or a half turn, or type an arbitrary angle and choose a colour for the corners it will expose.
3Apply the rotation; the pixels and the orientation flag are reconciled so every viewer agrees on which way is up.
4Download the rotated BMP file.
Rotate BMP FAQ
How does Rotate BMP turn the file?
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Concretely, the pixel array is transposed and written back exactly, so a rotation of a lossless image is free in fidelity terms at any right angle and costs only resampling at an arbitrary one. Quarter turns and half turns are the common case and take the cheapest path available for the format.
Can I rotate by an arbitrary angle, not just 90 degrees?
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Yes, though the two are different operations underneath. A multiple of 90 degrees rearranges existing data; any other angle has to rebuild the grid and fill the corners, so it costs a resample and usually wants a background colour choosing.
Does the format decide whether rotation is lossless?
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It does. BMP is essentially raw uncompressed RGB rows with a small header, so it is perfectly lossless and enormous — often 10-20x the size of the same image as PNG. That property is exactly what determines whether a quarter turn is free or costs a re-encode.
Anything specific to BMP I should know?
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Yes — because nothing is compressed, a BMP is fast to read and edit but punishing to upload, and it carries no metadata to preserve. It is the kind of thing that explains why a file looks right in one application and wrong in another.
Why does my file look correct on my phone but sideways elsewhere?
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Because the orientation is stored as an EXIF flag rather than in the pixels, and not every viewer honours it. Rotating here normalises the two — the pixels and the flag end up agreeing, so the file looks the same everywhere.
Can I rotate a whole batch in one go?
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Yes. The same rotation is applied across every file you upload, which is the practical fix for a folder of scans or camera output that all came in the wrong way round.
What can I upload to Rotate BMP?
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PNG, BMP and TIFF are the lossless raster formats this handles directly, and lossy sources (JPG, WebP, GIF) work too if you want them in the same batch. Multi-page TIFFs are detected and handled page by page.
Is there a file size limit on Rotate BMP?
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Yes: free accounts process images up to 5 MB each; lossless sources hit that ceiling sooner than photographs do, because nothing has been thrown away yet. If you are over it, converting to PNG first is often enough on its own — a BMP is routinely ten to twenty times the size of the identical image as PNG.
Will Rotate BMP lower the quality of my BMP images?
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No. A lossless source round-trips bit-exactly, so unless you explicitly ask for a lossy output format the pixels that come back are the pixels that went in. That is the whole reason to keep working in this family while you are still editing.
Can I run Rotate BMP on several BMP images at once?
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Yes — upload the set and they process in parallel under one set of settings. Lossless files are larger, so a big batch is bound by your upload speed rather than by the processing itself.
Does the alpha channel survive?
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Yes. PNG and TIFF carry a full 8-bit alpha channel and it is preserved end to end. It is only flattened if you deliberately target a format that has no alpha, in which case transparent pixels are composited onto white.
Does Rotate BMP cost anything?
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No. Rotate BMP runs free without an account and adds no watermark. Files are removed from the workers shortly after you download, and nothing about the image is retained.
