You are not going to get a single, clean winner here. Among the big, global CDNs, uptime is effectively a photo finish. The same names keep coming up: Akamai, Cloudflare, Fastly, Amazon CloudFront, Google Cloud CDN, and a couple of smaller players like CacheFly and Bunny.
If you really forced me to crown “most reliable uptime” from recent data, CloudFront and Akamai often sit at the very top of measured availability, with Fastly, Google Cloud CDN and Cloudflare so close that the difference is fractions of a minute of downtime per month.
So in practice, if you pick from that top tier and architect things properly, you are unlikely to lose sleep over CDN uptime alone. The real choice becomes: which one fits the rest of your stack, budget and control needs, not “who has one extra nine”.
How To Think About CDN Uptime
When you ask “Which CDN has the most reliable uptime”, what you really care about is:
- How often users get your content successfully
- How bad things get when that CDN has a bad day
Vendors describe this using two things:
- SLA uptime percentage
This is the promise on paper. For example, 99.9 percent, 99.99 percent or “100 percent” uptime, usually per month. - Real-world measured uptime
This is what independent monitoring and RUM (real user monitoring) actually see over months.
The difference between 99.9 and 99.99 looks tiny, but it is not. At 99.9 percent, you can be down around 44 minutes per month. At 99.99 percent, that shrinks to about 4 minutes.
Once you start talking about 99.999 percent, you are into “a few minutes per year” territory. That is where the top CDN providers are competing now, at least according to multi-vendor benchmark reports.
When someone says “we have the fastest CDN” or the “best content delivery network”, they are often mixing speed (latency) with availability (uptime). Those are related but not the same thing, and you want to look at both.
Uptime SLAs Of The Major CDN Providers
Let me walk you through what the major CDN providers actually put in writing. I am simplifying a bit here; each SLA has long legal sections and caveats.
A few important things you probably care about more than the raw numbers:
- “100% uptime SLA” does not mean they will never go down. It means they give you credits if they do. Cloudflare, Akamai, Fastly and CacheFly all use this model for certain plans.
- CloudFront and Google Cloud CDN are more conservative on paper, but independent data shows their actual availability is often equal or better than some 100% SLA peers.
- SLAs usually exclude a lot of things: your own origin failing, certain network events, “maintenance”, force majeure and so on. The credits rarely cover your real business loss, they just signal how confident the vendor is.
So if you line up the major CDN providers based on marketing SLAs, several “win” with 100 percent uptime guarantees. Once you line them up based on measured data, the picture gets more nuanced.
What Independent Data Says About Real Uptime
You do not want to just trust vendor slides. This is where third‑party monitoring and CDN ranking sites come in.
A couple of useful sources:
- CDNPerf tracks both performance and “rum uptime” for dozens of CDNs, based on billions of real user tests and synthetic probes.
- CloudHarmony and similar platforms have historically compared cloud and CDN availability across providers and regions.
- Some vendors (like BlazingCDN in their big 2025 report) aggregate Catchpoint, Pingdom and RUM data to produce their own “most reliable CDN” ranking.
From that BlazingCDN meta-analysis, here is the interesting bit: over a recent 12‑month window, Akamai, Cloudflare, Fastly, Amazon CloudFront, Google Cloud CDN, Bunny, Gcore and others all sit extremely close to 99.999 percent measured uptime.
CloudFront edges ahead slightly in their dataset, with Akamai, Google and Fastly basically tied right behind, and Cloudflare just a hair below them.
That is why I said at the top that you are really splitting hairs. You are arguing over seconds or a couple of minutes of downtime per month at worst.
“Fastest CDN” vs “Most Reliable CDN”
One more nuance that trips people up: fastest CDN is not always the one with the best uptime graph.
For example, a 2025 comparison that leans heavily on CDNPerf data calls Bunny “the fastest CDN” globally in terms of response time, but notes that it ranks only 13th when you sort by uptime.
So if you are chasing pure speed, your CDN ranking will not be the same as if you are chasing absolute uptime. The top CDN providers are close on both metrics, but they are not identical.
So Which CDN Is “Most Reliable” In Practice?
If you put everything together, here is how I would frame it to you as a tech person:
- There is a top reliability pack, not a single undisputed champion.
Akamai, Amazon CloudFront, Google Cloud CDN, Fastly and Cloudflare repeatedly show five‑nines‑ish availability in external reports and RUM data. - From published numbers, CloudFront and Akamai often come out slightly ahead.
CloudFront has slightly higher documented measured uptime in at least one 2025 comparison, despite a more modest 99.9 percent SLA. Akamai backs parts of its platform with 100 percent availability SLAs and very mature operations. - Cloudflare, Fastly, Google Cloud CDN and CacheFly are so close that your users will not notice the difference.
All of them operate with 100 percent uptime SLAs on certain tiers or near‑perfect measured availability, plus large global networks and proven operational history. - Some “newer” providers (Bunny, Gcore, BlazingCDN, Edgio, etc.) are starting to match the big guys.
Their real-world uptime is extremely close to the incumbents, often with lower cost.
Who Has the Most Reliable Uptime
Pick from Akamai, CloudFront, Fastly, Google Cloud CDN or Cloudflare and architect your stack well. If you want to squeeze the last few seconds of availability out of the system, lean toward CloudFront or Akamai, or run a multi‑CDN setup across two of them.
That is the level at which differences really start to matter.
To keep things actionable for you, here is a quick checklist focused entirely on uptime:
- Pick a vendor from the top CDN providers group: Akamai, CloudFront, Google Cloud CDN, Fastly, Cloudflare, plus possibly a second “value” CDN like Bunny or Gcore as backup.
- Make sure their SLA and network footprint align with your real traffic regions, not just globally.
- Treat multi‑region origins and health checks as mandatory, not “nice to have”. A rock‑solid CDN still fails if your origin is the single weak link.
- Use external uptime monitoring on your own domain, not only vendor status pages.
- If uptime is truly mission‑critical, run multi‑CDN and accept the complexity in exchange for another nine.
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