How CDNs Use Client-Side Code to Speed Up Web Downloads
Amazon's patent on using client-side code like JavaScript to dynamically rewrite website links so they point directly to the fastest content delivery server, bypassing traditional DNS routing bottlenecks.
Original patent title: “Network resource identification”
Amazon's patent on using client-side code like JavaScript to dynamically rewrite website links so they point directly to the fastest content delivery server, bypassing traditional DNS routing bottlenecks. Granted to Amazon Technologies Inc in 2017 with 22 claims and 69 forward citations.
Key facts
Coverage
What does this patent actually cover?
The patent describes a system where a Content Delivery Network or CDN provides executable code to a user's web browser. When the browser loads a webpage, this code runs and requests translation information from the CDN for original URLs embedded in the page. The CDN determines the best server source based on factors like regional plans or service levels, and sends back translation rules. The browser then rewrites the original URLs into optimized URLs pointing directly to the CDN's chosen server and fetches the assets. For example, a standard link like 'example.com/image.png' is dynamically rewritten by the browser into a CDN-specific link like 'cdn-region1.service.com/image.png' before the browser makes the request.
The gap
What does this patent NOT cover?
- Does not cover traditional DNS-based redirection where the domain name resolution itself redirects the user without client-side code execution.
- Does not cover URL rewriting performed entirely on the origin server before the webpage is sent to the client.
- Does not cover static URL structures where links are hardcoded and never dynamically translated or updated by client-side scripts.
- Does not cover client-side translation that does not involve requesting translation rules from an external service provider.
These exclusions are unique to PatentBrief — derived from the actual claim language, not patent-office boilerplate.
What made this novel
Instead of relying on DNS servers to guess where a user is located, the system uses the user's own browser to ask the CDN for a personalized routing map, dynamically rewriting the webpage's links on the fly.
Schematic visualization of the patent's claim structure. Hand-drawn diagrams in progress for each landmark patent.
Where you've seen this
Real-world examples
Amazon CloudFront CDN routing
Dynamic client-side asset optimization in modern web applications
Edge-computing-driven URL rewriting in browsers
Why it matters
The bigger picture
In high-performance web hosting, routing users to the nearest server is critical. Traditional DNS routing can be slow and is often cached incorrectly by internet service providers. By moving the routing logic into the browser using JavaScript, CDNs like Amazon CloudFront can bypass DNS limitations, making websites load faster and allowing real-time traffic management based on service tiers or regional outages.
Filed
November 19, 2014
Granted
January 10, 2017
Market context
Who's building on this
Companies in this space
Amazon Web Services utilizes these client-side routing and edge-computing techniques within its CloudFront CDN. Competitors in the CDN and edge-worker space, such as Cloudflare and Fastly, also deploy client-side scripting and edge-side rewrites to optimize asset delivery and bypass DNS propagation delays.
Market impact
This technology helped shift CDN architecture from rigid DNS-level routing to highly dynamic, client-assisted routing. It enabled more granular traffic control, allowing web platforms to implement complex regional routing and service-level agreements directly within the user's browser session.
Claim 1 — Plain English
What this patent covers
The patent describes a system where a Content Delivery Network or CDN provides executable code to a user's web browser. When the browser loads a webpage, this code runs and requests translation information from the CDN for original URLs embedded in the page. The CDN determines the best server source based on factors like regional plans or service levels, and sends back translation rules. The browser then rewrites the original URLs into optimized URLs pointing directly to the CDN's chosen server and fetches the assets. For example, a standard link like 'example.com/image.png' is dynamically rewritten by the browser into a CDN-specific link like 'cdn-region1.service.com/image.png' before the browser makes the request.
The clever bit
Instead of relying on DNS servers to guess where a user is located, the system uses the user's own browser to ask the CDN for a personalized routing map, dynamically rewriting the webpage's links on the fly.
What it does not cover
- Does not cover traditional DNS-based redirection where the domain name resolution itself redirects the user without client-side code execution.
- Does not cover URL rewriting performed entirely on the origin server before the webpage is sent to the client.
- Does not cover static URL structures where links are hardcoded and never dynamically translated or updated by client-side scripts.
- Does not cover client-side translation that does not involve requesting translation rules from an external service provider.
Patent timeline
Application submitted to the patent office
Application published, typically 18 months after filing
Patent officially issued
PatentBrief Score
Impact Score
High impact
Citation count
37/40
Highly cited
Claim breadth
15/20
Broad claimsclaimsThe numbered statements at the end of a patent that legally define what the inventor owns.Read more →
Recency
10/20
Granted 5–10 years ago
Assignee scale
20/20
Major company or institution
PatentBrief Impact Score — based on citation count, claim breadth, recency, and assignee scale. Not a legal assessment.
Heuristic Value Estimate
What this patent might be worth
$410K – $1.3M
Midpoint $819K · 8.4 yr remaining · industry ×1.4
Heuristic only — blends forward/backward citation counts, claim scope, time remaining, litigation history, and CPC-derived industry baseline. Real valuations need a professional appraisal.
The original legal language
Original claims
22 claims as filed with the patent office.
Concepts involved
Citations
Patent lineage
Cite this patent
Cormie, J., Sivasubramanian, S., Richardson, D. R., Pope, E. E., Scofield, C. L., & Marshall, B. E. (2017). How CDNs Use Client-Side Code to Speed Up Web Downloads (U.S. Patent No. 9,544,394). U.S. Patent and Trademark Office. https://patentbrief.org/patent/us/9544394/aws-cloudtrail
Auto-generated from the patent record. Double-check author order and the issue date against the official USPTO document before submitting.
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Common Questions
Frequently Asked Questions
What does How CDNs Use Client-Side Code to Speed Up Web Downloads cover?
Amazon's patent on using client-side code like JavaScript to dynamically rewrite website links so they point directly to the fastest content delivery server, bypassing traditional DNS routing bottlenecks.
Who owns patent US 9544394?
Amazon Technologies Inc owns this patent, granted in 2017.
When does this patent expire?
This patent is expected to expire on January 10, 2037, when the invention enters the public domain.
What is patent US 9544394 cited by?
This patent has been cited by 69 later patents that build on its ideas.
What problem does this patent solve?
In high-performance web hosting, routing users to the nearest server is critical. Traditional DNS routing can be slow and is often cached incorrectly by internet service providers. By moving the routing logic into the browser using JavaScript, CDNs like Amazon CloudFront can bypass DNS limitations, making websites load faster and allowing real-time traffic management based on service tiers or regional outages.
What does this patent NOT cover?
Does not cover traditional DNS-based redirection where the domain name resolution itself redirects the user without client-side code execution.
Same assignee
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