Flip an image horizontally

A horizontal reflection reverses each row of the picture and leaves the columns alone. In matrix terms it is a scale of minus one on x with a translation of the frame width; in practical terms it is the cheapest thing a raster editor can do, because no value is recomputed and only the addresses change. The output is the same set of samples in a different order, which is why doing it twice returns the file you opened.

It is also the reflection with the largest visible consequences, because writing runs horizontally. Lettering in shot stops being readable immediately, and that single effect splits the people who want this operation into two groups: those printing onto transfer paper, for whom unreadable is the correct intermediate state, and everyone else, for whom it means the wrong tool was reached for.

1. 1Open the file. Drop it, pick it, or paste it. The reflection is already applied when the panels appear, because this page opens on the horizontal axis.
2. 2Check what moved. Drag the divider across the frame, or hold Space to see the original at full width. Anything that appears to jump between the two panels is a detail that reversed.
3. 3Save it. Choose the container, then Save mirrored file. The full-resolution pass calls the same function the panel called.

The same decoders serve every page here: JPG, PNG, WebP, AVIF, GIF, BMP, TIFF and ICO natively where the browser allows it, HEIC through a codec fetched on demand. Exports are JPEG, PNG or WebP, defaulting to the container you brought. EXIF and the ICC profile are copied across for JPEG and PNG, with the orientation flag reset to one so that no viewer applies a second transform on top of the one you just approved.

• A reversed photograph misrepresents the scene. Every asymmetric detail is now on the wrong side. If the picture will be used as a record of what happened, of who was holding what, or of what a sign said, a horizontal reflection makes it wrong in a way that is very hard to spot later.
• The file is rewritten even though the samples are only rearranged. A JPEG saved as a JPEG is compressed a second time. The reflection itself costs nothing; the encode does. Save to PNG if the source was a JPEG and the grid has to survive exactly, and accept a much larger file for it.

Is a horizontal flip the same as a mirror image?

In this context, yes. Horizontal flip is what the operation is called in software; mirror image is what the result is called by the people who have to live with it. Both mean the samples in each row read out in the opposite order.

Which details change sides?

Everything asymmetric. Text and numbers first, then watches, wedding rings, hair partings, shirt buttoning, the side a bag is carried on, guitar handedness, steering wheels, and every sign, badge or plate that happened to be in frame. Faces are the quiet one: most are asymmetric enough that a reversed portrait looks subtly unfamiliar to anyone who knows the person.

Will a horizontal flip fix a photograph that came out sideways?

No, and this is the most common reason people arrive at a reflection tool by mistake. A picture recorded sideways needs turning, which moves samples between rows and columns; a reflection only reverses them within a row. Reflecting a sideways photograph gives you a sideways photograph that is also backwards.

Does the pixel data change at all?

The values do not; their positions do. Reflecting the same file twice on this axis returns the original grid exactly. What can differ is the file on disk, because a JPEG has to be compressed again on the way out unless you save to PNG instead.

Can I reverse only part of the picture?

Not on this page. Choosing a region and reflecting that alone is a compositing job rather than a transform, and it is not built here. Mirroring one half onto the other is the nearest thing this site does, and it has its own page.