Image Preparation topic guide

Image upload checklist: what to check before you upload

Direct answer

Open the file properties first. Confirm width and height, format, byte size, aspect ratio and whether the image has transparency. Then match those facts to the destination: a platform Help page when one exists, or a display-size decision for a normal website. Only after that decide whether to resize, crop, convert or compress — and never stretch the image to force a size.

Try the Image Preparation

What this workflow handles

Most upload failures are predictable. A file fails a marketplace check because the longest side is below the documented minimum, the format is outside the accepted set, or the file exceeds a published byte limit. A website image wastes bandwidth when it is far larger than the rendered display size — Chrome for Developers' Properly size images audit flags that case. Format choice for the open web is covered by MDN's image type guide (JPEG, PNG, WebP and related formats). Amazon Seller Central, Shopify Help and Etsy Help publish the marketplace numbers this checklist points to; Meta's link-share image docs cover Open Graph previews. Where a destination has no reliable official size table, treat the size as unknown and set custom dimensions instead of guessing a 'best size'.

Use Image Preparation to analyze one upload, check documented requirements with sources, prepare without stretching, then re-validate the real output. For a single operation only, open Image Compressor, WebP Converter, or a marketplace resizer instead.

If you already know the dimensions are wrong or the bytes are too high, start with Resize vs Compress.

How to use it

  1. Read the file: width, height, format, bytes, aspect ratio, transparency.
  2. Open the destination's official Help / Seller docs (or decide display size for a normal website).
  3. Label each field Required, Recommended, Informational or Unknown — never invent a number.
  4. If dimensions are too large for the use case, resize or letterbox; if the ratio must match a fixed frame, crop/cover only with eyes open to edge loss.
  5. If the format is wrong for the destination, convert; if bytes are still too high, compress / re-encode.
  6. Re-check the actual output file (dimensions, format, bytes) before you upload.
  7. Optional: run the same sequence in Image Preparation so checks and prepare share one sourced ruleset.

Frequently asked questions

What should I check before uploading an image?

Five facts on the file itself: pixel width and height, format (JPEG, PNG, WebP, and so on), file size in bytes, aspect ratio, and whether alpha/transparency is present. Then compare those facts to the destination's documented rules. If the destination has no official rule for a field, mark it unknown — do not invent one.

How do I know if I should resize, crop, convert or compress?

Too many pixels for the destination → resize (downscale) or letterbox onto a canvas. Wrong aspect for a fixed frame and you are willing to lose edges → crop/cover. Wrong format for the destination → convert. Dimensions are fine but bytes are still too high → compress or re-encode. These operations solve different problems; Chrome for Developers separates 'properly size images' from 'efficiently encode images' for the same reason.

Should I stretch an image to match a target size?

No. Stretching changes the aspect ratio and distorts the subject. Prefer letterboxing (keep the full image, add padding) or cover cropping (fill the frame, trim edges) when the source ratio does not match the canvas. If crop would remove important content, keep letterbox or choose a different target size.

Is there one official maximum file size for website images?

No. MDN and related web standards describe formats and delivery patterns, not a single global KB cap for every website image. Platform Help pages (Shopify product media, Meta link shares, and others) do publish destination-specific byte limits — use those when they exist.

What do Amazon, Shopify and Etsy require?

Use each platform's own Help page. Examples of documented technical limits: Amazon Seller Central states accepted formats and a longest-side range of 500–10,000 pixels for product images, with JPEG preferred and a pure-white main-image background; Shopify Help states product/collection images up to 5000×5000 and under 20 MB, with 2048×2048 usually best for square photos; Etsy Help lists accepted shop image types and listing-photo size guidance. Category style guides and policies can add more rules — re-read the current official page before you upload.

When should I use Image Preparation instead of a single resizer?

Use Image Preparation when you are unsure which checks apply and want sourced PASS / WARNING / FAIL / UNKNOWN results before and after processing. Use a dedicated Amazon, Shopify or Etsy resizer when you already know the destination and only need that canvas. Use Image Compressor or WebP Converter when dimensions are already correct and you only need a smaller or different-format file.

Does checking transparency matter?

Yes when the destination or format cannot keep alpha. JPEG has no transparency; PNG and WebP can. Flattening onto white is common for Amazon main images (pure white RGB 255,255,255 is documented for main images). If you need a clear background later, keep a PNG/WebP with alpha until the last step.

Sources

Explore the image preparation topic cluster

This guide covers the inspection step before upload. Related decision guides cover resize vs compress, web optimization, and marketplace pipelines.

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