Image optimisation comes down to four things: compress and size images properly, use a modern format, write alt text for people, and give files descriptive names. The first is worth the most, because oversized images are the leading cause of slow pages and slow pages cost calls.
Size and compression, which is most of the value
A photograph straight from a phone is several megabytes and several thousand pixels wide. Displayed in a 600 pixel column, every one of those extra pixels is downloaded and discarded.
Two separate operations, and people frequently do only one:
- Resize to roughly the dimensions it will actually display at, allowing for higher-density screens.
- Compress, which reduces file size at a quality setting where the difference is not visible.
Doing both routinely takes a page from unusable to fast, and it is the single change that most often resolves the problems described in how slow before calls drop.
Formats
| Format | Use for |
|---|---|
| WebP | The sensible default for photographs and graphics. Broad support, substantially smaller than JPEG at equivalent quality. |
| AVIF | Smaller again, with slightly less universal support. Worth using with a fallback. |
| JPEG | Still fine, and the safe fallback where compatibility matters. |
| PNG | Only where transparency or sharp-edged graphics require it. Poor choice for photographs. |
| SVG | Logos, icons, and line graphics. Scales perfectly and is usually tiny. |
The common error is a PNG photograph, frequently several times the size of the same image as WebP or JPEG with no visible benefit.
The technical pieces worth having
- Width and height attributes on every image. This reserves the space before the image loads, preventing the layout shift that pushes content around under the reader. It is a one-line change with a measurable effect.
- Lazy loading for images below the fold, so they download as the reader approaches rather than all at once.
- Do not lazy load the main image at the top. A common mistake that delays the largest visible element and worsens the metric you were trying to improve.
- Responsive images, where you can, so a phone receives a smaller file than a desktop.
Filenames
A modest signal, and free.
"IMG_4471.jpg" tells nothing. "cast-iron-drain-replacement-langley.jpg" describes the image in words. Use hyphens, keep it short, describe the content honestly, and do not stuff keywords into it, which produces filenames that read as spam and contribute nothing.
Worth doing on upload, since renaming later means changing every reference.
Alt text
Covered properly in alt text that is actually useful, and the short version bears repeating here because it is routinely written for the wrong audience.
Alt text exists for people who cannot see the image. Describe what the image contributes, keep it to about a sentence, use an empty attribute for decorative images, and do not write it for search engines. The search benefit follows from accurate description; writing it for machines produces text that fails the people it exists for.
Where images pay off
The return on image work is mostly indirect, and it is larger than the direct effect suggests.
Image search matters for some businesses more than others, and for a local service business it is rarely the main channel. That is not where the value sits.
Handled well, images make pages faster, demonstrate real work as argued in before and after galleries, and keep readers on the page long enough to make contact. Those effects compound, which is why image handling is worth doing properly rather than treating as an afterthought.
The priority order is unambiguous: fix the file sizes, use a modern format, write proper alt text, then tidy the filenames. Each step adds to the last, and a site that has done all four loads faster and reads better than one that stopped at the first.
The check
Open your gallery page on a phone with wifi off and count the seconds. Then look at the file size of your largest image.
If any single image is over about 300 kilobytes, that is where to start, and the improvement on a gallery-heavy site is usually immediate and visible.
Frequently asked questions
What is the most important part of image optimisation?
Resizing and compressing images properly. Photographs uploaded straight from a phone are several megabytes and several thousand pixels wide, and every excess pixel is downloaded then discarded, which makes oversized images the leading cause of slow pages.
Which image format should I use?
WebP is a sensible default for photographs and graphics, with broad support and substantially smaller files than JPEG at equivalent quality. AVIF is smaller again with slightly less support, JPEG remains a safe fallback, and SVG suits logos and line graphics.
Why should images have width and height attributes?
Because they reserve the correct space before the image loads, preventing the layout shifting under the reader as images arrive. It is a one-line change per image with a measurable effect on both experience and page experience metrics.
Should all images be lazy loaded?
No. Lazy loading suits images below the fold so they download as the reader approaches, but applying it to the main image at the top of the page delays the largest visible element and worsens the loading metric you were trying to improve.
Do image filenames matter for SEO?
Modestly, and they are free to get right. A descriptive filename using hyphens communicates what the image shows, while a camera-generated name communicates nothing. Avoid stuffing keywords, which produces filenames that read as spam and contribute nothing.
Does image SEO bring traffic to a local business?
Rarely through image search directly, since few people find a tradesperson that way. Images help indirectly by keeping pages fast when handled well, demonstrating real work, and holding readers on the page, which matter more than image-specific optimisation.
West Coast Media Solutions Inc. builds websites for businesses across Canada. Search and analytics platforms change frequently, and where practitioners genuinely disagree we have said so rather than presenting one position as settled.
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