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cdnjs Review

Worth it

Should I use cdnjs?

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

· 1 month ago

Use it if you need a free, zero-maintenance way to serve popular open-source libraries — Cloudflare's network makes it dependable. Skip it if you are privacy-sensitive, compliance-bound, or mission-critical; self-hosting beats any public CDN there.

Confidence

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

Ratings

  • Value for money
  • Ease of use
  • Feature depth
  • Support quality
  • Security posture

Pricing

$0

Free

ModelNot disclosed
Monthly fees250B
HardwareNot disclosed
Free tierYes

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

Gotchas - check before you buy

high

Supply-chain concentration: one cdnjs compromise reaches every site using it — 2021 proved the risk

medium

Cross-domain scripts share visitor IPs with Cloudflare; GDPR teams must assess lawful basis

medium

No SLA, contract, or paid support — volunteer-run open-source project

medium

Security writers increasingly argue public CDNs add risk without benefit; self-hosting is the trend

Pros and cons

Pros

  • Free forever, no usage caps
  • Runs on Cloudflare's global edge network
  • 12.5% of all websites rely on it
  • HSTS preloaded with strong transport defaults
  • Default library CDN in Core templates

Cons

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

Sources & method

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

official x2review x7security x3
  • 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.

Key stats

  • Value for money: 5/5

    Rating

  • $0

    Starting price

  • 12

    Sources

  • Analyzed

  • Value for money: 5/5. Free forever, no caps, Cloudflare-powered
  • Ease of use: 4/5. Copy-paste script tags; ASP.NET Core default
  • Feature depth: 3/5. Huge catalog; static library files only
  • Support quality: 2/5. Community-run open source; no SLA
  • Security posture: 3/5. HSTS preloaded, but 2021 RCE history
  • 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

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 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
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.

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

Methodology

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

Read how a report is made.

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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