When you need to rotate an image
The most common case is the simplest: a photo taken sideways that a viewer or upload form displays wrong. Phone cameras record orientation in the file's metadata, and while most software respects it, some strips or ignores it, leaving an image rotated ninety degrees. A quarter turn fixes it.
Fine rotation solves a different problem — straightening a horizon or a document that was photographed at a slight angle. A few degrees is often all it takes to turn a slightly-off shot into a level one, and the eye is surprisingly sensitive to a tilted horizon even when it cannot immediately say what is wrong.
Rotation and flipping are different
Rotating turns the image around its centre. Flipping mirrors it, swapping left and right (horizontal flip) or top and bottom (vertical flip). They are not interchangeable, and the distinction matters.
A horizontal flip is useful for correcting selfies, which front cameras often mirror, or for changing which way a subject faces in a composition. But flipping any image containing text renders the text backwards and unreadable, which is the one thing to watch for — a horizontal flip of a photo with a sign or label in it will reverse the writing.
Why the canvas grows when you rotate
Rotating a rectangle by anything other than a multiple of ninety degrees means its corners now extend beyond the original bounding box. To avoid clipping those corners, the canvas here expands to fit the rotated image, which is why a forty-five degree rotation produces a larger canvas with transparent triangles in the corners.
This is the correct behaviour — the alternative would cut off parts of your image. If you need a rectangular result after a fine rotation, crop the straightened image afterwards to remove the transparent edges.
Quality
Ninety-degree rotations and flips are lossless operations. They simply reassign pixels to new positions without inventing or discarding any, so the image quality is identical to the original. This is worth knowing: rotating a photo a quarter turn costs nothing in quality.
Rotation by other angles is different, because pixels no longer map cleanly to a grid and the browser must interpolate, which introduces a very slight softening. It is imperceptible for a small straightening adjustment but worth being aware of if you rotate the same image repeatedly.
Output format
The tool outputs PNG, which is lossless and supports the transparency that appears in the corners after a non-right-angle rotation. If you rotate by a multiple of ninety degrees and want to keep the file small, converting the result to JPEG afterwards is reasonable since there is no transparency to preserve.
Nothing is uploaded
Rotation and flipping happen on a canvas in your browser. Your images are never transmitted, which matters for personal photos and documents.
Frequently Asked Questions
Does rotating reduce image quality?
Ninety-degree rotations and flips are lossless. Other angles require interpolation and cause a very slight softening, imperceptible for small adjustments.
Why does the canvas get bigger when I rotate?
So the corners of the rotated image are not clipped. The transparent triangles that appear can be cropped afterwards if you need a rectangle.
What is the difference between rotating and flipping?
Rotating turns the image around its centre. Flipping mirrors it. Flipping any image with text renders the text backwards.
How do I straighten a crooked photo?
Use the fine angle slider, which rotates by single degrees. A few degrees usually levels a tilted horizon.
Are my images uploaded?
No. Everything happens on a canvas in your browser and never leaves your device.