diff --git a/README.md b/README.md
index c4345522..65c4678a 100644
--- a/README.md
+++ b/README.md
@@ -304,6 +304,9 @@ The _frame_ in `eframe` stands both for the frame in which your egui app resides
 ### Why is `egui_web` using so much CPU in Firefox?
 On Linux and Mac, Firefox will copy the WebGL render target from GPU, to CPU and then back again: https://bugzilla.mozilla.org/show_bug.cgi?id=1010527#c0
 
+### Why does my web app not fill the full width of the screen?
+To alleviate the above mentioned performance issues the default max-width of an egui web app is 1024 points. You can change this by ovveriding the `fn max_size_points` of `epi::App`.
+
 
 ## Other
 
diff --git a/eframe/src/lib.rs b/eframe/src/lib.rs
index 25d08e4b..71c9edfb 100644
--- a/eframe/src/lib.rs
+++ b/eframe/src/lib.rs
@@ -35,6 +35,10 @@ pub use egui_web::wasm_bindgen;
 /// Install event listeners to register different input events
 /// and start running the given app.
 ///
+/// For performance reasons (on some browsers) the egui canvas does not, by default,
+/// fill the whole width of the browser.
+/// This can be changed by overriding [`epi::Frame::max_size_points`].
+///
 /// Usage:
 /// ``` no_run
 /// #[cfg(target_arch = "wasm32")]
diff --git a/egui_web/src/lib.rs b/egui_web/src/lib.rs
index 9571f942..b939344a 100644
--- a/egui_web/src/lib.rs
+++ b/egui_web/src/lib.rs
@@ -3,6 +3,11 @@
 //! This library is an [`epi`] backend.
 //!
 //! If you are writing an app, you may want to look at [`eframe`](https://docs.rs/eframe) instead.
+//!
+//! ## Specifying the size of the egui canvas
+//! For performance reasons (on some browsers) the egui canvas does not, by default,
+//! fill the whole width of the browser.
+//! This can be changed by overriding [`epi::App::max_size_points`].
 
 #![cfg_attr(not(debug_assertions), deny(warnings))] // Forbid warnings in release builds
 #![deny(