Fix oversized images and assets to speed up slow pages

Why slow pages usually come from oversized images and assets

Page weight is how many bytes your browser has to download before a page feels usable. That includes images, fonts, video, JavaScript (JS), CSS, and third-party scripts. The heavier the page, the longer people stare at a blank screen, especially on mobile.

Oversized images are the most common culprit because they're easy to miss. A hero image that is 4000px wide might look great, but if it's displayed in a 1200px area, you're paying for pixels nobody can see. On mobile, that cost shows up immediately: slower networks, higher latency, and less powerful devices turn big images into delayed first views and janky scrolling.

Large JS and CSS files slow things down in a different way. Even after the download finishes, the browser still has to parse and execute JS, and often process CSS before it can paint the page. So a page can "download fast" and still feel stuck.

"Looks fine on my laptop" is a trap. Laptops tend to have fast Wi-Fi, strong CPUs, and warm caches. Real visitors might be on a budget phone over 4G with nothing cached.

When you're reducing page weight, keep the goal simple:

• Download fewer bytes before the first view
• Make fewer requests (each request adds overhead)
• Avoid JS and CSS that block rendering
• Make repeat visits faster with caching

If your site was built quickly with AI tools and performance regressed, this pattern is common: uncompressed images plus oversized bundles that were never checked on real devices.

Find the biggest offenders in 10 minutes

Start by finding what's actually heavy on the page. Guessing wastes time because one giant image or a single bloated script can outweigh everything else.

Open your page in a normal browser window, then open DevTools and go to the Network tab. Refresh once with the Network tab open so it captures every request.

A quick routine that works on most sites:

• Sort requests by Size (or Transferred) and scan the top.
• Click the biggest images and compare their file size to how large they appear on screen.
• Watch for repeated assets (the same icon, background, or font downloaded multiple times).
• Note any single huge JS or CSS file that stands out.
• Write down the top 5 heaviest requests and what they are (image, JS, CSS, font).

When you inspect an image, look for mismatches like a 4000x3000 photo shown as a 400px-wide thumbnail.

Also watch for "death by a thousand cuts": dozens of small icons, backgrounds, and font variants that add up. If you see the same file name pattern repeated, you probably can consolidate.

If your top 5 includes two hero images over 2 MB each and one 900 KB JavaScript bundle, that's already a clear first pass. Fix those, and you usually feel the difference immediately.

Step-by-step: run a simple page weight audit

Capture a baseline first. Pick one slow page (often the homepage or a key landing page), then record four numbers: load time, total bytes transferred, number of requests, and the biggest single file. Save these "before" notes so you can prove the improvement later.

Next, open DevTools (Network tab) and reload the page with cache disabled. Sort by Size (or Transfer Size) to see what's actually heavy.

It helps to bucket the weight so you're not treating everything the same:

• Images (JPG/PNG/WebP/AVIF, hero banners)
• Fonts (often multiple weights you don't need)
• Video (autoplay backgrounds, large MP4s)
• JS and CSS (large bundles, source maps, unused libraries)
• Third-party scripts (chat widgets, trackers, A/B tools)

Then make a simple call for each big item: remove it or optimize it.

If an asset doesn't change what the user can do, try removing it first. A second icon set, a 1.5 MB background image behind text, or a marketing script no one checks can often go away. If it must stay, mark it for resizing, compression, splitting, or caching.

Start with the easiest win, usually the largest image above the fold. A single 3-5 MB hero image can add seconds to first load.

After each change, rerun the same test and compare against your baseline. If the numbers don't move, you fixed the wrong thing, or the asset is still being downloaded somewhere else.

Step-by-step: compress images without making them look bad

Most slow-page problems start with one mistake: someone uploaded a camera original. A phone photo might be 4000px wide and several MB, even though your site only shows it at 1200px.

1) Pick the right format first

Choosing the right format often saves more than any quality slider.

• JPEG: best for photos (small files, smooth gradients)
• PNG: use only when you need true transparency or crisp pixel art
• WebP or AVIF: great for most modern sites when you can serve them (often much smaller)

2) Resize before you compress

Export close to the biggest size the image will ever appear on your site. If your hero image displays at 1400px wide, don't upload a 5000px file and hope compression will fix it.

3) Lower quality in small steps

Export, check, then reduce again. Start high (around 80-85), compare at 100% zoom, then step down (75, 70, 65) until you can see a difference. Stop one step before it's noticeable to a normal viewer.

4) Strip hidden baggage

Many images include metadata (camera info, location data, editing history). Removing it can shave off extra KB with no visual change.

5) Make it repeatable

Agree on an export convention so everyone does it the same way. For example: page-section_subject_width.format like home-hero_team_1400.webp.

If you inherited an AI-generated codebase where images are scattered, duplicated, or imported in inconsistent ways, FixMyMess (fixmymess.ai) can help audit the asset pipeline so the smaller files you create are the ones that actually ship to production.

Step-by-step: serve responsive image sizes

Responsive sizing means small screens get small image files, and large files are reserved for cases that truly need them. It's one of the fastest wins without changing your design.

Pick a few standard widths you will generate for important images. For many sites, 480px (phones), 768px (tablets), and 1200px (desktop) cover most cases.

Match the file to the context. A grid of 12 products doesn't need 2000px photos. If an image is shown as a small card, use a real thumbnail that matches that card, not the full hero version.

Here's a simple pattern that works on many pages:

\u003cimg
  src=\"/images/product-768.jpg\"
  srcset=\"/images/product-480.jpg 480w,
          /images/product-768.jpg 768w,
          /images/product-1200.jpg 1200w\"
  sizes=\"(max-width: 600px) 480px,
         (max-width: 900px) 768px,
         1200px\"
  alt=\"Product photo\"
  loading=\"lazy\"
/\u003e

A few things to watch:

• Don't rely on CSS to shrink a huge image into a tiny box. The browser still downloads the huge file.
• Use real thumbnails in lists and grids, and reserve the largest size for detail pages or hero sections.
• Keep sizes honest. If sizes claims the image displays at 1200px on mobile, the browser may pick a larger file than needed.

Confirm it's working. Open the Network panel, reload the page, and click the image request. The downloaded file should change as you resize the window or test a phone-sized viewport. If the transferred size stays large, your srcset/sizes (or image URLs) likely don't match what the page actually displays.

Shrink heavy bundles (JS and CSS) that block loading

A bundle is the packed file your site sends to the browser, usually JS and CSS. Bundles start small, then grow as you add features, copy snippets, and install libraries. When they get too big, the browser has to download, parse, and run more code before the page feels usable.

Spot what's making the bundle huge

Bundle audits often point to the same causes:

• A big UI library imported for a single component
• Two libraries doing the same job (dates, charts, icons, state)
• Duplicated code across entry points or copy-paste
• "Dev-only" helpers accidentally shipping to production
• Whole modules imported when you only need one function

Once you see the biggest chunks, you can usually cut size without changing how the site looks.

Reduce what loads on first view

Start by removing dead weight that's safe to delete (unused pages, old components, abandoned experiments). Then split code so each page loads only what it needs. Your admin dashboard code shouldn't ship with the public homepage.

If something isn't needed for the first screen, delay it. Typical candidates include chat widgets, analytics extras, A/B testing, large animations, and rarely used UI.

A practical approach:

• Load page-specific code only on that route (code splitting)
• Replace heavy dependencies with lighter ones when possible
• Import only the parts you use (avoid "import everything")
• Defer non-critical scripts until after the first view

If the real slowdown is a giant JS bundle from an AI-generated prototype, FixMyMess specializes in diagnosing, repairing, and refactoring these codebases so they behave like production software instead of a demo.

Use caching headers so repeat visits feel instant

Caching lets the browser reuse files it already downloaded instead of fetching them again on every visit. After you reduce page weight, caching is how you keep the site feeling fast for returning users.

A safe rule: cache static files for a long time, and change the filename when the file changes. That's why versioned filenames (or "fingerprints" like app.3f2a1c.js) matter. When you ship an update, the filename changes, so the browser downloads the new file.

Practical defaults for most sites:

• Images, fonts, and hashed JS/CSS: Cache-Control: public, max-age=31536000, immutable
• Non-hashed assets (like logo.png that you overwrite): shorter caching, for example max-age=3600
• HTML pages: keep caching short (or use no-cache) if content changes often

HTML is the one people over-cache. If you set a long cache on your main page, users can get stuck on an old version even after you deploy.

To verify caching, do a hard reload once, then reload normally. In the Network panel, repeat loads should show tiny transfer sizes (often marked as memory or disk cache) for images, CSS, and JS.

Other common hidden weight: fonts, icons, video, and third-party scripts

Even after you cut the obvious stuff, pages can still feel slow because of "small" files that add up. Fonts, icon packs, background videos, and third-party scripts often load early and delay the page from feeling ready.

Fonts are a common trap. Each weight and style is a separate file, so regular + medium + bold + italic can quietly become hundreds of KB. Most sites only need one or two weights.

Icons can be worse. Shipping a whole icon library for 12 icons is like bringing a moving truck for a grocery run. Keep a tight set, or export only the icons you actually use.

Video is the heavyweight you notice last. A hero video that autoplays on mobile can blow up data usage and delay interaction. A safer default is a poster image first, then load the video only when the user taps play (or when you detect a fast connection).

Third-party scripts (analytics, chat widgets, A/B tests) can dominate load time because they often pull in even more scripts. If you must keep them, load them later and remove duplicates.

Quick checks that usually pay off:

• Cut font families and weights to the minimum that still looks good
• Replace giant icon packs with only the icons you use
• Disable autoplay video on mobile and start with a lightweight poster
• Audit third-party tags and delete anything no one uses
• Make sliders load only the first slide's images until the user interacts

Common mistakes that keep pages slow

Speed work often fails for one reason: you fix the symptom, not what the browser actually downloads.

"It's compressed"... but still way too big

Compression helps, but it doesn't fix serving the wrong dimensions. A 4000px-wide photo squeezed into a 600px card still forces a big download.

A quick gut check: if the image looks sharp at 2x zoom on a laptop, it probably doesn't need to be thousands of pixels wide.

Lazy-loading the wrong images

Lazy-loading is great for images far down the page. It often hurts when you apply it to above-the-fold images like the hero, logo, or first product shot. The browser waits, fetches late, and the page feels slower.

A practical rule: load the first screen normally; lazy-load what comes after the first scroll.

Caching can also backfire. If you set caching headers that are too sticky without proper versioning, visitors might never see updates (or you're forced to disable caching entirely). The safe pattern stays the same: cache static files for a long time, but change the filename when the file changes.

Two more mistakes that waste time:

• Optimizing one page while shared layout assets (global CSS, header scripts, large icons) stay huge and slow down every page
• Adding "optimization" tools and plugins that quietly increase bundle size more than they save, especially if they ship heavy JavaScript

If your app was generated by tools like Bolt, v0, or Replit, these issues can pile up quickly. Often, a few oversized shared assets do most of the damage.

Quick checklist before you ship

Right before release, do one last pass to confirm you actually reduced what the browser downloads during initial load.

Run a hard refresh, open the Network panel, and sort by Size. Focus on the first few requests and the biggest items.

Ship-ready checklist:

• Re-check the top 5 largest requests: none should be unexpectedly huge after your changes.
• Confirm the largest image is sized for its container (not uploaded at 4000px to display at 600px).
• Use a modern image format where it's supported (with a safe fallback if needed).
• Reload again and confirm caching works for static assets: repeat loads should transfer very little.
• Don't add new third-party scripts without measuring impact first.

A concrete check: if your hero section is 1200px wide on desktop, the biggest hero image request should be in that ballpark, not a multi-megabyte original. If it still is, your responsive sizing or export settings didn't stick.

Example: speeding up a slow homepage in a realistic afternoon

A founder ships a marketing homepage quickly, then notices a problem: on phones it feels stuck before anything becomes usable. The page looks simple, but it downloads far more than it should.

A quick check shows three offenders. The hero image is a 4000px-wide file served to everyone, even small screens. The "small" icons are actually large PNGs with no compression. And the site ships one big JavaScript bundle that blocks rendering because everything loads up front.

A practical order that usually produces fast wins:

• Resize the hero to a reasonable max size, then export a compressed version.
• Add responsive variants so phones get a smaller file than desktops.
• Convert and compress icons (often to SVG, or a well-compressed modern format).
• Split the main JS bundle so only critical code loads first.
• Add caching headers for static assets so repeat visits feel instant.

To confirm it worked, compare before and after on the same device and network. Look at total bytes downloaded, image bytes, and how long it takes until the first visible content appears. It's common to cut several megabytes and shave multiple seconds on mid-range phones.

Where it gets tricky: AI-generated codebases often duplicate assets in multiple folders or have messy build steps that re-introduce huge images on every deploy. If the build is fighting you, start by finding where those files are coming from, not just compressing them again.

Next steps if your codebase fights you

Sometimes you do all the right things and the project still feels slow or fragile. That usually means the problem isn't only files on disk. It's also how the app is built, bundled, and deployed.

Make one clear decision: do you need a quick cleanup or a deeper rebuild?

A quick cleanup is worth it when the page is mostly fine and you can point to a few heavy images, a single huge bundle, or missing cache rules. A deeper rebuild makes sense when every change breaks something, builds are inconsistent, or the bundle is so tangled that small fixes take hours.

If your app was generated by tools like Lovable, Bolt, v0, Cursor, or Replit, expect extra hidden bloat: duplicated libraries, unused components shipped to users, images imported in ways that bypass optimization, and build settings that disable minification or code splitting.

While you're touching build settings, treat it as a safety pass too. Speed work can expose bigger risks.

What to check while you optimize

A quick review should cover:

• Exposed secrets in client code or config files
• Broken or inconsistent authentication flows
• Unsafe input handling (for example, SQL injection risks)
• Third-party scripts added "just to test" and never removed
• Caching and compression settings that differ between local and production

If you want an outside set of eyes, FixMyMess can run a free code audit to pinpoint heavy bundles, unoptimized images, and risky shortcuts. If the codebase is fighting you, we can diagnose the issues, repair the logic, harden security, and prep the app for production so performance fixes don't create new bugs.