What does the rating mean?

A is well-optimized; F means the image is heavily oversized for its dimensions and format. Aim for A or B for production assets — that is the threshold where image weight stops being a Core Web Vitals problem on most pages.

What is a good compression score?

Above 80 (B grade). Anything below 60 needs immediate attention; below 40 is dragging your page-speed scores. The score weighs file size against image dimensions and assumed quality, so a 2MB hero photo gets penalized differently than a 2MB infographic with text.

Does this actually compress my image?

No — this tool only rates. Use the companion Image Compressor to actually reduce file size. The two together form a pipeline: rate to decide if compression is needed, compress to fix.

Why is my image rated low?

Common causes: PNG used for photos (should be JPEG or WebP), uncompressed export from design tool, unnecessarily high resolution for display size, or no compression applied at all.

Should I use WebP, AVIF, or stick with JPEG?

WebP is the safe default in 2026 — supported everywhere, ~30% smaller than JPEG at same visual quality. AVIF is newer, ~20% smaller than WebP, but support is still imperfect on older browsers. For new sites, WebP with JPEG fallback covers 99% of users.

How does image compression affect Core Web Vitals?

Directly. Largest Contentful Paint (LCP) is usually the hero image; if it is 2MB, LCP is poor. Compression cuts LCP in half on most pages. CLS and INP are less affected by image weight, but a slow-loading hero hurts overall user experience.

Will compression hurt visual quality?

Slightly, often imperceptibly. JPEG quality 75-85 is the sweet spot — visually indistinguishable from quality 100 but 30-50% smaller. Below 70 starts to show artifacts on photos. Test by saving the same image at different qualities and comparing side by side.

What if my hero image needs to be high quality?

Use a higher resolution + WebP at quality 85, then serve responsive sizes via srcset. The 4K version exists for retina displays; the 1.5K version serves regular screens. Net page weight stays low because each viewer downloads only the size their device needs.

How do I use this for SEO audits?

Run your top organic landing pages' hero images through the rater. Anything below B is a Core Web Vitals risk. Fix in priority order: highest-traffic pages first. The audit doubles as a quick wins list for performance optimization sprints.

Is the file size the only factor?

No. The rater also considers dimensions (a 200KB file at 4000x3000 is differently rated than 200KB at 800x600), format efficiency, and visual complexity. A simple icon at 50KB rates worse than a complex photo at 200KB.

Should I rate images before or after upload to CMS?

Both. Before upload to verify the source asset is acceptable; after upload via the CMS-served URL to confirm your CMS isn't adding extra overhead via wrappers, watermarks, or wasteful resizing.

What happens to images I upload?

Processed in-memory and discarded. We do not retain the file, do not log content, and do not associate the rating with the image after the request returns.

Free SEO Tool

Free Image Compression Rating Tool

Get an A-F grade and 0-100 score for any image. URL or upload, instant verdict, actionable advice. Free, no signup, page-speed-friendly.

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Used by 45,000+ developers

What the Compression Rating Tool does

Image weight is the #1 cause of slow pages. The Compression Rating Tool gives you a quick A-F grade for any image — the fast way to spot which assets need to be compressed before they hurt Core Web Vitals.

Paste a URL or upload a file. The algorithm weighs file size against dimensions and format efficiency. A means well-optimized; F means the file is heavily oversized for its purpose. Re-export, re-rate, ship.

How to rate an image

Five steps from image to optimized.

Pick URL or upload

Paste an image URL or upload a file directly.

Click Rate Image

The tool fetches the image, analyzes file size vs dimensions, and assigns a grade.

Read the verdict

See your A-F letter grade, 0-100 score, and a one-line verdict explaining the result.

Compress if needed

For C/D/F, run through the Image Compressor or re-export from your design tool.

Re-rate to verify

After compression, rate the new file. Aim for A or B.

When developers and SEOs use it

Six common workflows.

Pre-publish image QA

Rate every hero image before pushing a blog post live. Anything below B gets compressed first. Saves Core Web Vitals regressions.

Performance audit sprint

You inherited a slow site. Run hero images through the rater; the F-rated ones are the quickest wins.

CMS upload validation

Some CMSes silently re-encode images at upload. Rate the served URL after upload to verify nothing got worse.

Designer handoff QA

Confirm that exported assets from Figma or Photoshop meet web-readiness standards before they hit your CMS.

Newsletter image checks

Email clients have aggressive image-size limits. Rate before embedding to avoid clipping.

E-commerce product photo audit

Run every category page hero through the rater; A-rated catalogs load faster than F-rated ones, which translates to checkout conversion lift.

Platform-specific setup guides

How to deploy compression on the platforms most teams ship from.

WordPress

Install ShortPixel or Smush; rate before and after to verify the plugin is doing its job.
For new uploads, Media Library settings often allow auto-WebP conversion — enable it.
For old images, run the bulk optimizer; rate a sample of pages after to confirm.

Webflow

Webflow auto-converts uploads to compressed formats. Verify by rating the served URL.
For custom embeds, manually compress before uploading.
Use the Asset Manager to bulk-replace oversized assets.

Shopify

Shopify auto-resizes via {{ image | img_url }}. Use the right size in your template, not the original.
For lookbook and editorial assets, manually compress with WebP.
Rate served versions to confirm theme isn't serving the original at full size.

Next.js / React

Use next/image with the right priority and sizes attributes for srcset generation.
For external CDN images, configure remotePatterns and let Next.js optimize.
Verify with this rater after deploy.

Static site generators

Hugo, Jekyll, Astro all support image processing pipelines.
Configure auto-WebP and responsive srcset.
Spot-check post-build by rating a sample of generated images.

Grigora vs. other rating tools

Side-by-side feature comparison.

Capability	Grigora	PageSpeed Insights	TinyPNG	Free generators	Manual
Free + unlimited	Yes	Limited free	Free trial	Yes	Manual
A-F letter grade + score	Yes	Score only	Yes	No	No
URL or upload	Both	URL only	Both	URL only	Manual
Actionable verdict text	Yes	No	Yes	No	Manual
Considers dimensions + format	Yes	Size only	Yes	Size only	Manual
No signup	Yes	Account required	Account required	Yes	Yes
Result speed	<3 sec	<10 sec	<5 sec	<3 sec	N/A
Privacy: no file retention	Yes	Stored	Stored	Mixed	Yes

Common errors and how to fix them

Eight issues teams hit when optimizing image assets.

URL fetch fails

Cause: CDN blocks cross-origin or requires auth.

Fix: Save the image and use the Upload tab.

Low score on a small image

Cause: Format is wrong (PNG for photo) or quality setting is too high.

Fix: Re-export as WebP at quality 85 or JPEG at quality 80.

High score but page still slow

Cause: Multiple medium-rated images on the same page compound.

Fix: Audit every image on the page. Total page weight matters, not individual scores.

Same image rates differently each run

Cause: Algorithm has minor variance for ambiguous file types.

Fix: Run twice; take the average. Differences are usually within 5 points.

PNG photo rated D or F

Cause: PNG is lossless — bad for photos. Better for icons and screenshots.

Fix: Convert to JPEG or WebP for photos.

WebP image rated lower than expected

Cause: WebP at quality 100 is unnecessarily large.

Fix: Re-export at quality 85; visual difference is imperceptible.

Score is high but file is huge

Cause: Image dimensions are very large; the algorithm rates relative to dimensions.

Fix: Resize to actual display dimensions before serving.

Tool times out on large file

Cause: File over 10MB takes longer.

Fix: Pre-resize to under 5MB before uploading. Or use the Image Compressor first.

Original data from our 2026 image audit

Across 5,000 production images.

67 (C)

Average score across 5,000 production hero images we tested

24%

% of images rated D or F (need urgent compression)

1.2 sec

Median page-speed gain after compressing F-rated images

PNG used for photos

Most common Fail format

Frequently asked questions

Twelve answers covering image compression rating.

Related free tools

Other utilities that pair with the Compression Rating Tool.

Rate an image right now

URL or upload, A-F grade, copy-paste fix advice. Free, unlimited, no signup.

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