Why image SEO still moves the needle
Search engines read pages, but they also weigh how those pages perform and how their images are described. A blog full of gorgeous, unoptimized photos can rank worse than a plainer page that respects file size, correct dimensions, descriptive filenames, and honest alt text. None of this is exotic - it is a checklist, and most sites skip at least half of it.
Below are the five checks worth running before you publish anything with images, from a single product photo to a hundred-post blog archive.
Check one: file size, the weight your page pays for
Every kilobyte an image adds is a kilobyte a visitor's browser has to download before it can paint the page. Large photos - especially unedited camera exports - routinely weigh several megabytes, which is absurd for anything displayed at 800-1200 pixels wide. Aim for a size that still holds up on a phone screen, not one that survives a 400% zoom nobody performs.
Use Compress Images to bring hero and product shots down before they touch a live page, and reach for batch compression once you are optimizing more than a handful of files at a time.
Check two: dimensions that match the slot, not the source
A 4000-pixel-wide photo squeezed into an 800-pixel card still forces every visitor to download the full 4000-pixel file - the browser just displays it smaller. Export or resize to the actual rendered width (2x only if you deliberately serve retina assets), then compress. This single habit fixes more slow pages than any advanced technique.
Check three: filenames that describe, not obscure
"IMG_4821.jpg" tells search engines and screen readers nothing. "blue-canvas-sneakers-side-view.jpg" tells them exactly what the file contains. Keep filenames lowercase, hyphenated, and specific enough to be useful without turning into a keyword dump.
- Use hyphens, not underscores or spaces
- Include the product, subject, or context where relevant
- Avoid stuffing the same keyword into every filename on a page
Check four: alt text written for a person first
Alt text exists primarily for people using screen readers, and secondarily as a signal for search engines. Describe what is actually in the image - a person, a setting, a product feature - rather than a slogan. If the image is purely decorative, an empty alt attribute is the honest choice.
Check five: format choice
Where your CDN and audience support it, modern formats like WebP typically deliver smaller files than JPG or PNG at comparable visual quality. Keep JPG as a fallback for compatibility-sensitive contexts, and reserve PNG for graphics that genuinely need transparency or sharp edges.
Running the checklist in five minutes
- Pick one page with several images
- Note current file sizes and dimensions
- Resize with Resize Images where the source is oversized
- Compress with Compress Images
- Rewrite filenames and alt text before re-uploading
- Check embedded fields with Image Metadata if privacy or copyright matters
None of these checks require a redesign. Run them on your busiest pages first, then fold the habit into how new images get added going forward - the compounding effect on load time and findability is larger than any single post suggests.
Auditing an existing library, not just new uploads
New content is the easy part - it goes through the checklist once and moves on. The harder, more valuable pass is auditing what already exists. Pull a report of your heaviest images (most CMS and CDN dashboards can show this), sort by file size, and start with the worst offenders on your highest-traffic pages. A homepage hero at 6MB will move the needle far more than fixing fifty rarely visited archive images.
Old images also tend to carry the worst filenames and thinnest alt text, simply because the checklist did not exist yet when they were uploaded. Treat a library audit as a recurring quarterly task rather than a one-time cleanup - new contributors and rushed launches will always reintroduce a few violations, and catching them early is cheaper than a second full audit a year later.
Turning the checklist into a publishing standard
A checklist only works if it survives contact with a deadline. Bake the five checks into whatever process governs publishing - a CMS pre-flight step, a short line in a content brief template, or a review comment a second person is responsible for catching. Teams that treat image SEO as "something we know about" rather than "something we verify" tend to slide back into oversized, poorly labeled uploads within a month or two of any initial cleanup.
Picnie at Picnie. Writes about image automation, developer experience, and shipping product faster.