Choose the placement before choosing its size
A link-preview image, an ad and an ordinary photo can have different rules on the same service. Each preset states its context and source. Custom dimensions let you compare requirements from another platform without treating them as verified presets.
Keep the whole image preserves every edge and adds background where the shapes differ. Fill the canvas preserves proportions but crops the source at the center. The comparison reports scaling, background per side, source crop dimensions and percentage of source area removed. It never stretches the image.
Use the result in your editor
The CSV records the calculation at full numeric precision up to eight decimal places; the on-screen values are rounded for readability. Fractional crop positions describe geometry and may round to pixels in an editor. This tool previews and measures; use Instagram image resizer, YouTube thumbnail maker or the image editor to prepare the image itself.
Privacy and limitations
Optional PNG/JPG inspection is local, limited to 10 MiB and 12 million pixels. Browser EXIF orientation is applied; animated PNG becomes a still frame. Manual dimensions support 1–16,384 pixels per side. Editing source dimensions removes the photo preview so it cannot misrepresent the source. A failed upload preserves the previous photo and values. Cancel or a 30-second deadline discards obsolete decoding results. No automatic storage or uploads.
Dimensions do not establish file-size compliance, ad eligibility or quality. Platforms may recompress files and crop previews. Enlarging a source does not recover detail. Dated official recommendations can change; review the linked source and final platform preview before publishing.