CDN monitoring
CDN & Cache Issues Detection
Your CDN reports the request as a success. What it actually sent back is an error page, not your script. The browser refuses it, your checkout breaks, and your uptime tool sees nothing wrong. Sitewatch checks that every file on your page is really there and is the kind of file it claims to be — so CDN failures get caught instead of hidden.
- Detect when CDN edge nodes serve errors instead of your assets
- Catch files served as the wrong type, which browsers silently refuse
- Flag missing or erroring assets on CDN-served URLs
CDN delivery failure detected
Affected resources
- app.js -- MIME type text/html (expected application/javascript)6:00 AM
- vendor.css -- 404 Not Found6:00 AM
- hero-image.webp -- 200 OK6:00 AM
- fonts/Inter.woff2 -- 200 OK, correct MIME type6:00 AM
01The monitoring gap
Your CDN dashboard says healthy. Your visitors say broken.
| Scenario | Basic monitoring | Sitewatch |
|---|---|---|
| Right file, right type | Not checked | Every asset verified |
| CDN error detection | Origin looks fine | Checks what the CDN delivers |
| Every file accounted for | Only page-level ping | Every JS, CSS, and image checked |
| Redirect detection | Not checked | Asset redirect chains caught |
| False positive prevention | Single check | 2-of-3 retry confirmation |
| Post-deploy verification | Manual browser check | Automatic on next check cycle |
Right file, right type
- Basic monitoring:
- Not checked
- Sitewatch:
- Every asset verified
CDN error detection
- Basic monitoring:
- Origin looks fine
- Sitewatch:
- Checks what the CDN delivers
Every file accounted for
- Basic monitoring:
- Only page-level ping
- Sitewatch:
- Every JS, CSS, and image checked
Redirect detection
- Basic monitoring:
- Not checked
- Sitewatch:
- Asset redirect chains caught
False positive prevention
- Basic monitoring:
- Single check
- Sitewatch:
- 2-of-3 retry confirmation
Post-deploy verification
- Basic monitoring:
- Manual browser check
- Sitewatch:
- Automatic on next check cycle
02Why it matters
CDN failures are invisible to your server and devastating to your visitors
CDN delivery failures
A CDN node hands back an error page instead of your script, and reports it as a success. Your server logs look clean. The browser gets a web page where it expected code, refuses to run it, and your site breaks.
Files served as the wrong type
Browsers are strict about this. If a CDN sends your script labelled as a web page, the browser blocks it without complaint. No visible error for most visitors — just a page that does not work.
Missing assets on CDN
A deploy invalidates CDN cache but the new files are not there yet. Or a CDN region is out of sync. Assets return 404 while your origin server has them. Sitewatch checks from the outside, like your visitors.
Wrong content types
CDN misconfigurations can serve CSS as application/octet-stream, images with wrong headers, or scripts as plain text. Browsers handle each case differently, but the result is always broken functionality.
Asset redirects and chains
CDN routing rules can redirect asset URLs to error pages, login screens, or entirely different files. Sitewatch follows redirects and validates what gets served.
The gap between "up" and "working"
Your origin looks healthy. Your CDN looks healthy. But the version delivered to the browser is wrong. That is the gap between "up" and "working" that traditional monitoring ignores.
03What gets flagged
CDN and delivery issues Sitewatch catches
Wrong file, wrong type
- JavaScript served as text/html -- browsers block execution
- CSS delivered with wrong content-type headers
- Files that arrive labelled as the wrong kind of file after CDN routing
- Non-HTML content returned for pages that should be HTML
Status code and availability
- 404 and 410 errors on CDN-served asset URLs
- Server errors returned by CDN nodes
- Asset URLs redirecting to error pages or wrong destinations
- Missing assets after CDN cache invalidation or deploy
04How it works
How Sitewatch detects CDN issues
- 01
Fetch your page
Sitewatch fetches the page over HTTP from outside your infrastructure and parses the HTML to extract every referenced script, stylesheet, and image URL.
- 02
Check every asset
Every file the page needs is requested to confirm it is really there and is the kind of file it claims to be. This catches CDN nodes returning errors, the wrong content, or unexpected redirects.
- 03
Confirm with retries
Detected issues go through 2-of-3 retry confirmation. Transient CDN glitches are filtered out. Only persistent failures create incidents.
- 04
Alert with context
Confirmed failures alert you across your configured channels, naming the exact file, what came back instead of it, and which page is affected.
05What you get
Outcomes, not a feature list.
Catch the CDN serving something other than your site.
A CDN can report every request as a success while handing back a cached error page instead of your script. Your origin is healthy, your logs are clean, and the browser quietly refuses to run it. Sitewatch checks what came back.
6
Incident types detected
2-of-3
Retry confirmation
5–30 min
Check intervals
Is your CDN actually serving what you think it is?
Find out in 2 minutes. Free plan, no credit card required.
06FAQ
Frequently asked questions
It means the server sent the right file but labelled it as the wrong kind of thing — for example, sending your script labelled as a web page. Browsers are strict about this and will refuse to run it, so the page quietly breaks while your server logs show nothing but successful requests. The technical name for it is a MIME type mismatch.
Sitewatch opens your page and works out every file it needs. Each one is then requested to confirm it exists and arrives as the right kind of file. If a CDN serves an error, the wrong thing, or nothing at all, it is caught and reported with the exact file and what went wrong.
No. Sitewatch checks that each file is there and is the right kind of file, rather than inspecting what is inside it. That catches the most common CDN failures — files erroring, arriving as the wrong thing, or disappearing after a cache clear. It does not track file versions or compare contents between checks.
Sitewatch works with any CDN -- Cloudflare, AWS CloudFront, Fastly, Akamai, Vercel Edge, and others. It monitors what gets delivered to the browser rather than relying on CDN-specific APIs, so it works regardless of your infrastructure.
Checks run on a configurable schedule -- every 30 minutes on Free, down to every 5 minutes on Pro. You can also trigger a check on demand from the dashboard or via deploy hooks, ideal for verifying a CDN cache invalidation worked correctly.
07Explore more