sw-delta | An incremental cache for the web

No, I don't think so. This is just the beginning of the project. I'm looking for beta-testers. Chrome, Firefox and Opera. This is 59% of compatible browsers, according to Can I Use. It is designed as a progressive enhancement. Browsers that don't support Service Workers will redownload the full file as they've always done, while modern browsers will be able to ask for the delta only. The client-side should not be a problem. Your website needs to be served on HTTPS, this is a limitation built in the Service Worker API. Then you only need to load the service worker and it deals with everything. No other change is required on to the page. It's a bit more complicated. Your server needs to be able to handle delta requests and to compute them. For the moment, I only wrote a NodeJS library, called sw-delta-nodejs. But any other language should be able to run sw-delta. It could also become a module for Apache and Nginx. It's slow. Calculating the delta for a file such as angular.1.4.5-min.js (143KB) takes 500ms. This is why the delta files should not be re-generated for every user and should be cached server-side. The easiest is to use sw-delta behind a reverse proxy (or a CDN). This is pretty fast. The same angular.1.4.5-min.js file only takes 3ms to be regenerated from the delta. I've built a quick benchmark that measures the size of the delta files on a few famous libraries (testing for example jQuery being upgraded from v2.0.0 to v2.0.1). The average delta file is 14% of the normal file. But in fact, it all depends how often you deliver and how small are the changes you deliver. I'm using the diff-match-patch npm module, which is a NodeJS wrapper around google-diff-match-patch. Then I compress the output in a home-made format. I'm pretty sure some improvements can be achieved on the speed and weight, don't hesitate if you have some ideas and use the benchmark.js script to test them. Using Chrome's Network panel, you are able to see one request from the page to the Service Worker, and another request from the Service Worker to the server. Firefox is not as good as Chrome, it does not show the requests from the SW. ~~Because the Cache API does not allow the modification of a file before storing it into the cache.~~ It's actually possible and it will change soon (see issue #2). Yes, it is best to keep them all. But it won't stop working if some files get deleted so you can delete the oldest ones if you need some disk space. Currently, the only supported format is /some/path/name-version.ext. The version can be any string. I recommend changing the version only when the content is really modified, to avoid unnecessary requests. An md5 hash of the file makes a perfect version number.