A practical checklist: smaller files, stable layouts, and images Google can understand.
width and height to the <img> tag, lazy-load only images below the fold, and write alt text that describes the picture. You can do the first three steps free with our Resize Image and Image Compressor tools.Be realistic about this. Google says its ranking systems use Core Web Vitals as part of page experience, but it also says a good page experience does not override relevant, helpful content. Faster images will not rescue a thin page. What they do is stop a good page from losing visitors who give up while a 5 MB hero photo loads on a phone, and they remove a reason for a close competitor to edge ahead.
Images touch two of the three Core Web Vitals directly:
The third metric, Interaction to Next Paint (INP, which replaced First Input Delay in March 2024), is mostly about JavaScript, not images. All three are judged on real visits at the 75th percentile, so a fast test on your office Wi‑Fi does not prove much.
This is the biggest win and the most skipped step. A phone photo is often 4000 pixels wide or more, while a blog column might display it at 800 CSS pixels. The browser still downloads every pixel. Resize to about twice the displayed width (so it stays sharp on high-density screens): roughly 1600 pixels for an 800-pixel column, 1200 pixels for a product card that shows at 600. Do this before compressing; compressing pixels you are going to throw away wastes effort.
If the same image appears at very different sizes on mobile and desktop, export two or three widths and let the browser choose with srcset and sizes.
iPhone photos arrive as HEIC, which most browsers cannot display. Convert them first with HEIC to JPG, and switch formats in general with Convert Image Format.
For web photos, quality 75–85 is the usual sweet spot: the file shrinks a lot and the difference is hard to see at normal zoom. Go lower for thumbnails, higher for portfolio pieces. Our Image Compressor keeps your original format and transparency by default (you can switch the output to JPEG, WebP or PNG), applies phone rotation so portrait photos are not saved sideways, and has a max-size box so you can resize and compress in one pass. If an image is already well compressed and re-encoding would make it bigger, it gives you the original back and tells you, rather than handing you a larger file. There is also a short walkthrough for compressing an image for a website.
Always open the compressed file at 100% zoom and check faces, fine text and gradients before you publish. Numbers on a slider do not see artefacts; you do.
width and height (the image's real pixel size, or matching proportions). The browser then reserves the right space and the text does not jump, which protects CLS. CSS can still make the image responsive.loading="lazy" is great for images further down the page. Do not put it on the main image at the top, because it delays exactly the element LCP is waiting for.fetchpriority="high" to the main above-the-fold image tells the browser to fetch it early.<img> elements for content images. Google does not index images that only appear as CSS backgrounds.Google Images and regular search both read the context around a picture. The basics from Google's own image guidelines:
blue-ceramic-mug.webp instead of IMG_4821.jpg.Photos straight from a phone can also carry GPS coordinates in their metadata. If that matters for a picture of your home or office, check it with Image Metadata before you upload. Re-encoding with our compressor leaves that metadata out of the new file.
Run the page through Google's PageSpeed Insights. The lab section shows which element is the LCP and flags oversized or unsized images; the field section (when your site has enough traffic) shows what real visitors experience. Over the following weeks, the Core Web Vitals report in Search Console groups your URLs into good, needs improvement and poor. Expect that report to move slowly, because it is based on 28 days of real visits.
Our image tools run on the server, not only in your browser. Each file is uploaded over HTTPS, processed for that request, and discarded. There is no signup and no copy kept for later. See the privacy policy.
Does compressing images improve SEO? Indirectly. Smaller images help LCP and keep visitors from leaving slow pages, and Core Web Vitals are one of many signals. Relevance and helpful content matter far more.
Is WebP better for SEO than JPEG? Google indexes both. WebP helps only because it is usually smaller, so the page loads faster. A well-compressed JPEG is fine.
What size should a blog image be? About twice the width it is displayed at, so roughly 1200–1600 pixels wide for a typical article column, compressed to a few hundred kilobytes or less for a photo.
Should every image have alt text? Every meaningful image should. Purely decorative images can use an empty alt="" so screen readers skip them.