Suggest an editImprove this articleRefine the answer for “What performance problems does CSR have?”. Your changes go to moderation before they’re published.Approval requiredContentWhat you’re changing🇺🇸EN🇺🇦UAPreviewTitle (EN)Short answer (EN)CSR (Client-Side Rendering) offloads almost all the work onto the user's browser, which is convenient for development, but from a performance standpoint it has a number of systemic problems. **Key point:** the main problems are a long empty screen on startup, a heavy JavaScript bundle, UI blocking, slow data loading, and SEO difficulties.Shown above the full answer for quick recall.Answer (EN)ImageCSR (Client-Side Rendering) offloads almost all the work onto the user's browser. This is convenient for development, but from a performance standpoint this approach has a number of systemic problems. Let's go through the main ones. --- ## 1. An empty screen on the first load With CSR the server usually serves an almost empty HTML and a large JavaScript bundle. What happens: 1. JS loads 2. JS executes 3. Data loads 4. Only then does the content appear The user sees emptiness or a spinner for a long time. This directly hurts: - FCP - LCP - the first impression of the site --- ## 2. A large JavaScript bundle With CSR, often: - the whole application's code loads at once - even the code for screens that aren't used - a lot of third-party libraries Consequences: - a long JS download - a long JS parse and execute - load on weak devices Especially painful on mobile. --- ## 3. Blocking the browser's main thread JavaScript runs on the main thread. With CSR: - app initialization - component rendering - computations and effects all of this can block the interface. Result: - buttons don't respond to clicks - scrolling lags - the interface is "frozen" --- ## 4. A slow first render of the data Data in CSR is usually: - requested after JS loads - received asynchronously - causes repeated renders Because of this: - content "flickers" - there are many loading states - extra re-renders happen The user sees the loading process, not the result. --- ## 5. SEO problems Search bots: - handle heavy JS worse - may not wait for data to load - spend more resources per page As a result: - indexing is slower - part of the content may be skipped - rankings are lower than pages with ready HTML --- ## 6. Dependence on the device and the network CSR heavily depends on: - CPU power - amount of memory - internet quality What is fast on a MacBook: - can lag on a budget Android device Performance becomes unpredictable. --- ## 7. Difficulty of optimization For CSR to run fast, you have to manually: - set up code splitting - optimize data loading - fight extra renders - keep an eye on bundle size Without this, the app quickly degrades in speed. --- ## Summary The main performance problems of CSR: - a long empty screen at startup - heavy JavaScript - UI blocking - slow data loading - weak predictability across different devices - SEO difficulties That's exactly why modern frameworks try to **reduce the share of CSR or combine it with server rendering**, so the user sees content as early as possible.For the reviewerNote to the moderator (optional)Visible only to the moderator. Helps review go faster.