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PerformanceChecked through WebDiag API

Image Performance Checker

Enter a page URL to find images, detect formats and weight, see legacy JPEG/PNG, oversized assets, missing dimensions, and AVIF/WebP recommendations without a separate low-value PNG checker.

  • AVIF/WebP
  • Image bytes
  • Responsive markup
Online tool

Try the tool

Enter a URL: WebDiag will run a safe network check and show the result.

Network check through backend

For HTTP/SEO tools, the URL is sent to the WebDiag API, where SSRF protection, DNS/IP policy, and redirect limits are applied.

Reviewed: 2026-07-17
01

How to use it

  1. 1

    Paste a public page URL.

  2. 2

    WebDiag loads the HTML and safely inspects discovered image candidates.

  3. 3

    Review formats, known bytes, oversized images, responsive delivery, and lazy-loading.

02

What the tool can do

  • Finds img, srcset, picture/source, and social preview images in static HTML.
  • Classifies AVIF, WebP, JPEG, PNG, SVG, GIF, ICO, and unknown formats.
  • Recommends AVIF/WebP only as part of a complete image performance analysis.
03

Common use cases

  • Find heavy JPG/PNG images that should move to AVIF/WebP.
  • Check width/height and responsive image markup after a release.
  • Prepare image fixes before Core Web Vitals optimization.
04

How it works inside

Resources are checked through SafeHttpFetcher with SSRF protection and bounded limits.

This is not a separate AVIF/PNG checker, but a complete image performance tool.

05

Questions and answers

Should PNG always be replaced by AVIF?

No. Photos and heavy raster assets are usually AVIF/WebP candidates; SVG fits vector graphics, while PNG can be justified for lossless UI graphics.

Why is this not a full waterfall?

A full waterfall requires a browser/PageSpeed. This tool is a fast and safe static scan for the image layer.