Does a 90-degree turn need empty corners?

No. A quarter turn maps a rectangle exactly onto another rectangle with width and height exchanged. Empty wedges appear only at angles that are not multiples of 90 degrees.

Is the picture re-encoded?

For ordinary browser-readable formats, yes. The pixels are decoded, turned and written once in the chosen output format. The separate lossless-JPEG route explains the metadata-only repair that avoids re-encoding.

Why does this open clockwise?

Clockwise is the most common correction after a portrait scan arrives on its side. The left and 180-degree buttons remain beside it, and each new choice is rendered from the original rather than from the previous preview.

The turn is computed on this device; the file never leaves this tab.

Rotate a picture 90 degrees

A precise clockwise quarter turn on opening, with left and half turns beside it and no arbitrary-angle crop hidden in the operation.

The preview begins one quarter clockwise after a file opens. Width and height exchange places exactly.

Drop a photo, or paste one.If its orientation tag is lying, this page will say so before you touch a control.

Nothing to hand?

The angle slider, the quarter turns and the corner decision appear here once a file is open. Nothing is sent anywhere to make that happen.

What makes a quarter turn exact

A ninety-degree rotation changes pixel addresses without requiring the geometric compromise of a free angle. The first column becomes a row, the old width becomes the new height, and every source pixel has one destination. There are no triangular gaps to fill and no need to crop inward.

The browser still has to write a new image file for most inputs, which is why quality and metadata controls remain visible. The important part is that the image is rendered once from the source. Pressing right twice does not encode a first result and then encode that result again; it updates one quarter-turn value and the final save reads the original pixels.

Cases that look similar but are not

A sideways JPEG that looks correct in one viewer may have an EXIF orientation disagreement rather than physically turned pixels.
A scan needing the same quarter turn across a folder belongs in a reviewed batch workflow, not a blind repeat of a single-file button.
A horizon tilted by three degrees needs straightening, which introduces a crop-or-padding decision that a quarter turn never has.

Questions about the turn

Does a 90-degree turn need empty corners?: No. A quarter turn maps a rectangle exactly onto another rectangle with width and height exchanged. Empty wedges appear only at angles that are not multiples of 90 degrees.
Is the picture re-encoded?: For ordinary browser-readable formats, yes. The pixels are decoded, turned and written once in the chosen output format. The separate lossless-JPEG route explains the metadata-only repair that avoids re-encoding.
Why does this open clockwise?: Clockwise is the most common correction after a portrait scan arrives on its side. The left and 180-degree buttons remain beside it, and each new choice is rendered from the original rather than from the previous preview.