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Should I Use cdnjs?

cdnjs.com·Analyzed 4 hours ago··Based on 12 sources

cdnjs is the free, open-source CDN for the web's most popular libraries, globally cached on Cloudflare's network.

Worth it

Worth it

Use it if you need a free, zero-maintenance way to serve popular open-source libraries — Cloudflare's network makes it dependable.

Free, Cloudflare-backed CDN for popular JS/CSS libraries. Ideal for prototypes and small sites; self-host if privacy or uptime matter.

Confidence: Medium

12.5%

Market share

of all websites

250B

Monthly requests

served on Cloudflare's edge

$0

Price

free, no paid tier

1.7M+

Sites tracked

per Tomba directory

Value for money5

Free forever, no caps, Cloudflare-powered

Ease of use4

Copy-paste script tags; ASP.NET Core default

Feature depth3

Huge catalog; static library files only

Support quality2

Community-run open source; no SLA

Security posture3

HSTS preloaded, but 2021 RCE history

Pros

  • Free forever, no usage caps⁵
  • Runs on Cloudflare's global edge network²
  • 12.5% of all websites rely on it10
  • HSTS preloaded with strong transport defaults
  • Default library CDN in Core templates⁹

Cons

  • Critical 2021 RCE could have compromised sites loading its scripts⁴
  • Visitor IPs shared with a third party — GDPR questions⁷
  • Third-party dependency: your site breaks if cdnjs does⁸
  • Many hosted libraries barely maintained after publication
  • Users reported Bad Gateway errors fetching some libraries12

Gotchas

  • highSupply-chain concentration: one cdnjs compromise reaches every site using it — 2021 proved the risk⁴
  • mediumCross-domain scripts share visitor IPs with Cloudflare; GDPR teams must assess lawful basis⁷
  • mediumNo SLA, contract, or paid support — volunteer-run open-source project⁶
  • mediumSecurity writers increasingly argue public CDNs add risk without benefit; self-hosting is the trend⁸

Best for

  • Frontend devs serving popular JS/CSS libraries
  • Prototypes, demos, and small business sites
  • Docs and blogs wanting zero build tooling
  • Open-source projects distributing browser builds

Not for

  • GDPR-strict or privacy-sensitive sites — third-party scripts share visitor IPs
  • Mission-critical apps that cannot tolerate third-party outages — self-host
  • Private or custom code — cdnjs hosts public open-source libraries only
  • Teams needing SLAs or vendor support — none exists

Pricing

Free

$0

  • All popular JS, CSS, and font libraries
  • Served on Cloudflare's global network
  • No SLA or paid support tier

Security

Infrastructure is hardened (HSTS preloaded), but cdnjs suffered a critical RCE in 2021 — patched; concentration risk remains.

  • Critical RCE in cdnjs (2021)A remote code execution flaw could have let an attacker serve malicious scripts to the ~12% of sites relying on cdnjs. Cloudflare patched it quickly.⁴

What users say

Developers treat cdnjs as the dependable free default, but a vocal contingent now argues public CDNs create more risk than benefit.

“Public CDNs Are Useless and Dangerous”
— httptoolkit blog
“[AskJS] How do you feel about using public CDNs?”
— Reddit, r/javascript

Alternatives

Compare cdnjs with each alternative.

Google Hosted Libraries

Google's free CDN; smaller catalog of top libraries

Full analysis

Based on 20+ public sources including Cloudflare's engineering blog, security advisories, and developer forums. Snippets were truncated, so no formal review ratings exist.

Sources

  1. cdnjs official sitecdnjs.com
    official
  2. Migrating cdnjs to Cloudflare's Developer Platformblog.cloudflare.com
    official
  3. Cloudflare's Handling of an RCE Vulnerability in cdnjsblog.cloudflare.com
    security
  4. Critical Cloudflare CDN flaw allowed compromise of 12% of all sitesbleepingcomputer.com
    security
  5. cdnjs always free — FreeTier.cofreetier.co
    review
  6. CloudFlare vs cdnjs — StackSharestackshare.io
    review
  7. Legitimate interest and loading jQuery from CDN — Reddit r/gdprreddit.com
    review
  8. Public CDNs Are Useless and Dangerous — httptoolkithttptoolkit.com
    security
  9. Why by default Asp.Net Core references cdnjs — Stack Overflowstackoverflow.com
    review
  10. Usage statistics and market share of CDNJS — w3techsw3techs.com
    review
  11. CDNjs vs JSdelivr — GitHub issuegithub.com
    review
  12. htmx CDN Bad Gateway — Reddit r/htmxreddit.com
    review

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