Why do my images load so slowly or not at all on mobile?

Images usually load slowly on mobile because the files are far too heavy for a phone connection: the photo is the problem, not the phone. When an image doesn't appear at all, the cause is almost always a broken link, a format the phone's browser can't display (such as HEIC straight from an iPhone), lazy-loading set up badly, or a theme that hides it on small screens. If images are missing on every site you open, check your phone or connection, not the website.

You open your site on your phone, wait, and the photo of your product shows up late, loads in strips or stays a blank square. On your laptop everything looks fine, but your customers are on their phones, often on mobile data, out on the street or in a waiting room.

The good news: each of these problems has a concrete cause, and most can be fixed without rebuilding the site. Start with the table below to see which case you're in, then read the matching section to check it yourself, even if you're not technical.

Quick diagnosis: what you see and what it usually means

Cause 1: the photos are far too heavy

The most common cause has nothing to do with the phone and everything to do with the photo. A modern camera or phone produces images of several megabytes each. Upload one straight to the site, exactly as it came off the phone, and the mobile browser has to download that whole file over a connection that's often much slower than home wi-fi.

How to check: save the photo from the site to your computer and look at the file size. If a single image is measured in megabytes rather than kilobytes, it's too heavy for the web.

What it should be: a photo prepared for the web usually weighs a few hundred kilobytes at most, is saved in a modern format (WebP or AVIF) and is resized to the width it's actually displayed at. It looks the same and loads far faster.

Two details that often get missed:

• The phone gets the desktop version. A well-built site keeps several sizes of each photo and lets the browser pick the right one (that's what srcset and the picture element are for). If the theme only has one big version, every phone downloads the file meant for a wide monitor.
• No width and height declared. Without them, the browser can't reserve space for the image, so the text jumps around while photos arrive. Google's guidance is to add width and height attributes to every image.

The practical steps are in our guide on how to optimize images for the web without losing quality.

Cause 2: a "broken" image (wrong link, moved file or http address)

When you see a blank square, a broken-image icon or just some text where the picture should be, it isn't a speed problem, it's a dead link. The page asks for the photo, but the file isn't at that address.

Typical causes:

• The file was deleted, renamed or moved to another folder after publishing.
• The photo was hosted on another site or an account that no longer exists, or that site blocks its images from being shown elsewhere.
• The address has capital letters or spaces written differently from the real file (many servers treat Photo.JPG and photo.jpg as two different files).
• The image address starts with http:// while your site runs on https://. Browsers try to upgrade such images to https automatically, but block them in some cases, for example when the image is set through a list of responsive sizes (srcset) or the picture element, or when it is requested from an IP address instead of a domain name.

Quick test: on the phone, press and hold the empty spot and open the image in a new tab if that option appears; on a laptop, right-click it. If you get an error page instead of the photo, the link is the problem. Another tell: missing on both phone and laptop, in every browser, almost always means a broken link.

Cause 3: a format the phone's browser can't display

This one confuses a lot of people, because the photo looks perfect on the phone you uploaded it from.

• HEIC photos from an iPhone. iPhones often save photos as HEIC (HEIF). Safari only displays this format from version 17, while Chrome, Firefox and Edge don't display it at all. Upload a HEIC file without converting it and you'll see it on your iPhone, while visitors on Android see an empty space. Export the photo as JPEG before uploading or, for photos meant for the site, switch the camera to Settings > Camera > Formats > Most Compatible.
• AVIF or WebP with no fallback. Modern formats are the right choice, but Safari only supports AVIF from version 16, so an older iPhone stuck on iOS 15 or earlier may show a blank. The safe setup serves AVIF or WebP with a JPEG fallback through the picture element, which is what good optimization plugins do.

Cause 4: lazy-load set up too aggressively

Modern sites use lazy-loading: images further down the page aren't downloaded right away, only as you scroll toward them. Done right, it saves data and speeds up the first view.

The trouble comes when it's badly configured. On a phone, where you scroll quickly with your thumb, the photo doesn't have time to arrive, so it stays blank for a second or two and then pops in, especially on a slow connection.

Google's guidance is clear: don't lazy-load images that are visible as soon as the page opens, and above all not the large image at the top (often the element LCP is measured on, the metric for how fast the main content appears). Some optimization plugins and themes apply lazy-load to every image, including the top one, and that produces exactly this delay.

Sliders and galleries that load their photos with a script are another weak spot: if the script fails or an optimization setting holds it back, those images can stay blank on the phone.

The fix isn't to switch lazy-load off entirely, but to load the first image straight away (no lazy-load, high priority) and let the rest load as the visitor scrolls.

Cause 5: the theme hides the image on mobile, or a cache shows an old version

• Hidden on mobile. Many themes and page builders let you hide a section on small screens or set a separate image for mobile. If that mobile image was never chosen, or a "hide on mobile" switch was left on, the photo exists on desktop and simply isn't there on the phone. Check the section's responsive or mobile settings in your editor.
• An old copy in a cache. If you replaced a photo and still see the old one (or a broken one), a copy may be stored in your browser, in a cache plugin or on a CDN. Clear the site's cache from the plugin or your hosting panel, then check again in a private tab.

If images don't load on any site, check your phone first

If photos are missing on every site, not just yours, the website isn't the problem. A few quick checks:

• Switch between wi-fi and mobile data to rule out a weak or filtered connection.
• Turn off any VPN, ad blocker or content blocker for a moment and reload the page.
• Rule out data-saving settings during the test. On Android it's usually Settings > Network & internet > Data Saver (names vary by manufacturer); on iPhone, Low Data Mode is under Settings > Cellular (Mobile Data in some regions) > Cellular Data Options, or in the info screen of the wi-fi network you're connected to.
• Clear the browser's cache or open the page in a private tab; if nothing changes, restart the phone.

How to check your own site in a few minutes

• Open the site on your phone on mobile data, not wi-fi. That's what your real customer sees.
• Save a few photos and check their file size. Megabytes per image is a clear signal.
• Compare devices: missing on the laptop too, in every browser? Broken link. Shows on the laptop but lags on mobile? Size or lazy-load. Shows on an iPhone but not on Android? Format.
• Run the page through PageSpeed Insights on the Mobile tab. Look at "Improve image delivery" (images too heavy, too large or in an old format) and "LCP request discovery" (whether the main image is lazy-loaded or found too late).

These checks usually point to one of the causes above without guesswork. If the score itself worries you, here's how to raise your PageSpeed Insights score without being a developer.

What to do next

If it's just a few photos, you can resize, compress and convert them yourself with a free tool, then upload them again. If the whole site is full of heavy images, or you see blank squares in several places, it's more than an evening's chore and worth doing properly.

That's how we work at MPO Web Studio, a small web studio in Cluj-Napoca: we prepare images in modern formats with a fallback, at the right sizes for phones, and set up lazy-load so the first photo appears straight away and the rest follow smoothly. We work remotely, with prices stated clearly up front, and for new clients we first build a free demo version so you can see the result before you decide.

If you like, send us a WhatsApp message with your site's address and we'll tell you honestly which of these problems you have and how long it would take to fix.