Image Optimization
An image file named IMG_1234.png is a blank space in a search engine’s reading of the page around it. Ivan Sp audits and corrects how a site’s images are named, formatted, and compressed. Images carry a real signal instead of a default camera filename. This work covers image-level fixes, and it stops short of the server engineering that full page speed work requires.
Descriptive Filenames Instead of Camera Defaults
A default filename such as IMG_1234.png tells a search engine nothing about what the image shows. Renaming to a clear, hyphenated name, such as blue-sofa.png, gives crawlers a signal alt text alone does not fully replace, particularly for image and visual search.
At volume, filenames get generated to a fixed specification rather than reviewed one at a time. One batch produced 100 filenames for a dental client under an exact rule set: three to four words, lowercase, hyphen-separated, under 20 characters, no file extension in the name string itself.
Format and Compression
I audit image format and compression level page by page. An oversized, uncompressed image is one of the most common and most fixable causes of slow load time. A modern format at an appropriate compression level cuts file size substantially with no visible quality loss in most cases.
Lazy loading gets applied to below-the-fold images, so a page does not spend load time on images a visitor has not scrolled to yet.
Image Sitemaps for Image-Heavy Sites
Sites carrying large volumes of product or gallery images benefit from a dedicated image sitemap, which helps search engines discover and index images that standard crawling might otherwise miss.
The sitemap gets built where image search is a genuine traffic source, meaning e-commerce catalogues and visually driven service businesses, not every site by default.
Where This Work Stops
I state the boundary plainly. Image-level fixes reduce load weight and improve discoverability. They are not the same service as full Core Web Vitals engineering. Server response time and hosting configuration need a developer with server access, and that distinction is explained on what this consultancy does not include.
Where an audit finds hosting is the actual limiting factor, the finding gets reported honestly. Image work alone cannot solve a hosting problem.
What This Looks Like in a Catalogue
Consider a furniture retailer whose photography budget last year ran to five figures. Every product shot is excellent and none of them appears in image search.
She paid for those photographs to sell furniture. Watching them sit unfound while cheaper competitors show up is not what that budget was for.
I export every image with its filename and alt attribute. All 480 are named DSC and none carries a description, so nothing that reads text knows what any of them shows.
Where the Standard Image Advice Breaks Down
- The usual advice
- Compress the images, add alt text with the target keyword, and the image work is finished.
- What holds up in practice
- Compression addresses weight and leaves discovery untouched. Filename, dimension attributes, and an image sitemap decide whether an image is found at all, and none of the three is a compression setting.
Picture a retailer who runs every product photograph through a compression plugin and sees the page weight halve. Nothing else changes.
The files are still named DSC_0492.JPG, still served at four times their display size, and still absent from any sitemap. The plugin did exactly what it promised.
I treat the filename as content rather than as a technical detail. A keyword in alt text helps far less than a filename that describes what the photograph actually shows.
The cost is a catalogue of correctly compressed images that no image search will ever surface.
Four Things Commonly Assumed About Image SEO
What is the filename of the main image on your most important page?
Ivan Sp meets these four assumptions on almost every catalogue engagement.
| Commonly assumed | What actually holds |
|---|---|
| Compression is the whole job. | Compression addresses weight. Filename, alt text, dimension attributes, and an image sitemap decide whether an image is found at all. |
| Alt text should contain the target keyword. | Alt text should describe what the image shows. A keyword appears naturally when the image genuinely depicts it, and forcing one helps nobody. |
| Every image needs alt text. | Decorative images need an empty alt attribute. Describing a divider line forces a screen reader to announce something with no value. |
| Serving a large image is safe because the browser resizes it. | The browser resizes after downloading the full file. A 4000 pixel image in a 600 pixel slot transfers the whole file every time. |
| Missing width and height attributes are a cosmetic issue. | Missing dimensions cause the layout to shift during load, which is measured directly by Cumulative Layout Shift. |
A catalogue of compressed images with camera filenames stays invisible to image search. Image search is where a large share of product discovery starts.
Image Reference Values
- Formats Google Images accepts
- JPEG, PNG, WebP, AVIF, GIF, SVG, and BMP.
- Modern format benefit
- WebP and AVIF usually reach the same visual quality at a smaller file size than JPEG.
- Filename guidance
- A short descriptive name using hyphens, such as walnut-dining-table-oval.jpg.
- Alt text purpose
- A plain description of the image, written first for screen reader users.
- Layout stability
- Explicit width and height attributes prevent the layout shift measured by Cumulative Layout Shift.
- Responsive delivery
- The srcset and sizes attributes let a browser choose a file matched to the viewport.
- Deferred loading
- The loading attribute set to lazy defers images below the fold.
- Image sitemap
- The image namespace extension to XML sitemaps, using image:image and image:loc elements.
A Worked Example: One Product Image, Before and After
Consider a furniture retailer with 480 product photographs exported straight from a camera. The values below are illustrative and show what changes on a single image. They are not drawn from a client engagement.
| Attribute | Before | After |
|---|---|---|
| Filename | DSC_0492.JPG | walnut-dining-table-oval-seats-six.jpg |
| Format and size | JPEG at 3.4 MB | WebP at 210 KB |
| Dimensions served | 4000 by 3000 for a 600 pixel slot | 1200 by 900 with srcset variants |
| Alt text | Empty | Oval walnut dining table seating six, shown from the side |
| Dimension attributes | Absent | width and height set in the markup |
| Sitemap entry | None | Listed in an image sitemap beside the product URL |
I treat the filename and the alt text as content rather than as metadata chores. Both describe the subject, and both are read by systems that cannot see the picture.
A photograph with no filename and no alt text is a slide with the caption torn off. The audience still sees it, and nobody taking notes can record what it showed.
Multiply that 3.4 MB saving across 480 images and the transfer weight of the catalogue changes substantially, which is the part a crawler notices first.
How an Image Pass Runs
I work in the order below, because renaming files after the sitemap is built creates a second round of work.
- Crawl the site and export every image URL with its file size, dimensions, and alt attribute.
- Sort that export by file size, and treat anything above roughly 200 KB as a conversion candidate.
- Flag every image whose rendered dimensions are far smaller than the file actually served.
- Rename default camera filenames to short hyphenated descriptions before any conversion runs.
- Convert candidates to WebP or AVIF, keeping a JPEG fallback where an older browser matters.
- Write alt text describing the subject plainly, and leave decorative images with an empty alt attribute.
- Add explicit width and height attributes in the template, which stabilises layout during load.
- Apply loading set to lazy below the fold, and leave the main above-fold image loading normally.
- Generate an image sitemap for catalogue or gallery sites, then submit it in Search Console.
- Re-crawl after deployment, and confirm no images remain above the agreed size threshold.
How This Work Is Scoped
I scope image work against image count rather than page count.
- What arrives
- A crawl export listing every oversized or undescribed image, plus corrected filenames and alt text.
- Typical duration
- One to three weeks, depending on image volume and whether renaming needs redirects.
- What the client supplies
- Media library access, and the original high-resolution files where conversion is needed.
- Included
- Audit, renaming plan, alt text writing, format recommendations, and image sitemap generation.
- Not included
- Photography, retouching, CDN configuration, and server-side image processing pipelines.
- What changes the estimate
- Catalogues above roughly five thousand images, or a platform that blocks filename changes.
- How it is quoted
- After a short scoping call, once image count and platform are known.
Tools and Primary Sources
The references below define the behaviour this work relies on. Each opens in a new tab.
- Google image SEO guidance sets out filename, alt text, and placement guidance for Google Images.
- Image sitemap specification documents the image namespace elements a sitemap can carry.
- Cumulative Layout Shift explains why missing dimension attributes cause a measurable layout penalty.
- Responsive images reference documents how srcset and sizes let a browser select an appropriately sized file.
Check Your Own Images in Five Minutes
I suggest a quick check on the page carrying your most important image.
- Open the main image in a new tab, then read its filename in the address bar.
- Check whether that filename describes the subject or repeats a camera default.
- Open your browser developer tools, select the Network tab, and reload the page.
- Sort the requests by size, and note any single image above 500 KB.
A camera default filename and a multi-megabyte transfer on the same image is the common pattern. Both are fixable without touching the photograph itself.
Common Questions
Does alt text count as part of image optimization?
Alt text is written separately, since it serves accessibility and description rather than file-level performance, and it is covered under image alt text writing. Both services usually run together on the same image set.
Which image format is most SEO-friendly?
Modern formats such as WebP typically produce the smallest file size at comparable visual quality. The right choice still depends on browser support requirements and the platform’s own image handling.
Will renaming existing image files break anything?
Breakage is possible when the old filenames are referenced elsewhere without a redirect. Renaming live images gets paired with 301 redirects from the old file paths, so existing links still resolve correctly.
Should every image on a page carry alt text?
No. Alt text describes images that carry meaning, and a purely decorative image should carry an empty alt attribute instead. An empty attribute tells a screen reader to skip the image rather than announce a filename.
Discuss This Work
The first call is a free 30-minute consultation with no pitch attached. You receive an honest assessment of where the site stands and what can realistically be built.