How to avoid page rendering delays in PHP and JavaScript web development?

The only practical tip is: open Developers Console, Network tab, and check the timeline. Then investigate the slowest calls

Just to add one thing, control how often the browser request e.g. pages, scripts and CSS files by setting the Cache-Control header. Endpoints that does not change that often can be cached in the browser (quicker) whereas more dynamic content should be requested each time it is needed. See more detailed description of HTTP caching.

A would advise against mindless caching. As a part of wider approach of optimizing something that is not slow. Instead, profile your app first, then optimize the actual bottleneck, for which caching would be just one of many strategies

1. Add UI loaders - much better then just staring at blank page. There is no way to have dynamic content render instantly.


2. Add server-side output compression for data to travel faster.


3. If it's SPA, consider pre-loading some content.


4. normalize.css if used to reset browser custom styles, so that your elements would look the same on all browsers - not performance related, does not improve CSS rendering


5. For back-end - there may be lots of things:

• Caching


• Database indexes


• Working in-memory and not fetching data from disc/database


• Optimised code execution