diff --git a/Cargo.lock b/Cargo.lock
index 1a85c8b54b23..c93b19ca821e 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -2871,6 +2871,15 @@ dependencies = [
  "winapi",
 ]
 
+[[package]]
+name = "ntapi"
+version = "0.4.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "bc51db7b362b205941f71232e56c625156eb9a929f8cf74a428fd5bc094a4afc"
+dependencies = [
+ "winapi",
+]
+
 [[package]]
 name = "num"
 version = "0.4.0"
@@ -3894,6 +3903,7 @@ dependencies = [
  "re_format",
  "re_log",
  "smallvec",
+ "sysinfo",
  "wasm-bindgen",
 ]
 
@@ -4822,6 +4832,20 @@ dependencies = [
  "unicode-xid",
 ]
 
+[[package]]
+name = "sysinfo"
+version = "0.28.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f69e0d827cce279e61c2f3399eb789271a8f136d8245edef70f06e3c9601a670"
+dependencies = [
+ "cfg-if",
+ "core-foundation-sys",
+ "libc",
+ "ntapi",
+ "once_cell",
+ "winapi",
+]
+
 [[package]]
 name = "system-deps"
 version = "6.0.3"
diff --git a/crates/re_memory/Cargo.toml b/crates/re_memory/Cargo.toml
index b05c08c9b61a..9e9a765140d9 100644
--- a/crates/re_memory/Cargo.toml
+++ b/crates/re_memory/Cargo.toml
@@ -33,6 +33,7 @@ smallvec = "1.10"
 [target.'cfg(not(target_arch = "wasm32"))'.dependencies]
 backtrace = "0.3"
 memory-stats = "1.0"
+sysinfo = { version = "0.28.3", default-features = false }
 
 # web dependencies:
 [target.'cfg(target_arch = "wasm32")'.dependencies]
diff --git a/crates/re_memory/src/lib.rs b/crates/re_memory/src/lib.rs
index 44b4701c78a3..2dcfc69d2b79 100644
--- a/crates/re_memory/src/lib.rs
+++ b/crates/re_memory/src/lib.rs
@@ -7,6 +7,7 @@ mod allocation_tracker;
 mod memory_history;
 mod memory_limit;
 mod memory_use;
+mod ram_warner;
 pub mod util;
 
 #[cfg(not(target_arch = "wasm32"))]
@@ -23,7 +24,7 @@ use backtrace_web::Backtrace;
 
 pub use {
     accounting_allocator::AccountingAllocator, memory_history::MemoryHistory,
-    memory_limit::MemoryLimit, memory_use::MemoryUse,
+    memory_limit::MemoryLimit, memory_use::MemoryUse, ram_warner::*,
 };
 
 /// Number of allocation and their total size.
diff --git a/crates/re_memory/src/ram_warner.rs b/crates/re_memory/src/ram_warner.rs
new file mode 100644
index 000000000000..989cdeedc48c
--- /dev/null
+++ b/crates/re_memory/src/ram_warner.rs
@@ -0,0 +1,61 @@
+/// Amount of available RAM on this machine.
+#[cfg(not(target_arch = "wasm32"))]
+pub fn total_ram_in_bytes() -> u64 {
+    use sysinfo::SystemExt as _;
+
+    let mut sys = sysinfo::System::new_all();
+    sys.refresh_all();
+
+    let total_memory = sys.total_memory();
+
+    re_log::debug!(
+        "Total RAM: {}",
+        re_format::format_bytes(sys.total_memory() as _)
+    );
+
+    total_memory
+}
+
+/// Amount of available RAM on this machine.
+#[cfg(target_arch = "wasm32")]
+pub fn total_ram_in_bytes() -> u64 {
+    1_u64 << 32
+}
+
+// ----------------------------------------------------------------------------
+
+pub struct RamLimitWarner {
+    total_ram_in_bytes: u64,
+    limit: u64,
+    has_warned: bool,
+}
+
+impl RamLimitWarner {
+    pub fn warn_at_fraction_of_max(fraction: f32) -> Self {
+        let total_ram_in_bytes = total_ram_in_bytes();
+        let limit = (fraction as f64 * total_ram_in_bytes as f64).round() as _;
+        Self {
+            total_ram_in_bytes,
+            limit,
+            has_warned: false,
+        }
+    }
+
+    /// Warns if we have exceeded the limit.
+    pub fn update(&mut self) {
+        if !self.has_warned {
+            let used = crate::MemoryUse::capture();
+            let used = used.counted.or(used.resident);
+            if let Some(used) = used {
+                if 0 <= used && self.limit <= used as u64 {
+                    self.has_warned = true;
+                    re_log::warn!(
+                        "RAM usage is {} (with a total of {} system RAM). You may want to start Rerun with the --memory-limit flag to limit RAM usage.",
+                        re_format::format_bytes(used as _),
+                        re_format::format_bytes(self.total_ram_in_bytes as _),
+                    );
+                }
+            }
+        }
+    }
+}
diff --git a/crates/re_viewer/Cargo.toml b/crates/re_viewer/Cargo.toml
index 33d7c73da078..24a2c6ff4694 100644
--- a/crates/re_viewer/Cargo.toml
+++ b/crates/re_viewer/Cargo.toml
@@ -99,8 +99,8 @@ rfd = "0.11"
 serde = { version = "1", features = ["derive"] }
 slotmap = { version = "1.0.6", features = ["serde"] }
 smallvec = { version = "1.10", features = ["serde"] }
-time = { workspace = true, default-features = false, features = ["formatting"] }
 thiserror.workspace = true
+time = { workspace = true, default-features = false, features = ["formatting"] }
 uuid = { version = "1.1", features = ["serde", "v4", "js"] }
 vec1 = "1.8"
 wgpu.workspace = true
diff --git a/crates/re_viewer/src/app.rs b/crates/re_viewer/src/app.rs
index cbc71213c532..1d17fa48e7c9 100644
--- a/crates/re_viewer/src/app.rs
+++ b/crates/re_viewer/src/app.rs
@@ -57,6 +57,7 @@ const MAX_ZOOM_FACTOR: f32 = 4.0;
 pub struct App {
     build_info: re_build_info::BuildInfo,
     startup_options: StartupOptions,
+    ram_limit_warner: re_memory::RamLimitWarner,
     re_ui: re_ui::ReUi,
 
     /// Listens to the local text log stream
@@ -127,6 +128,7 @@ impl App {
         Self {
             build_info,
             startup_options,
+            ram_limit_warner: re_memory::RamLimitWarner::warn_at_fraction_of_max(0.75),
             re_ui,
             text_log_rx,
             component_ui_registry: Default::default(),
@@ -416,6 +418,11 @@ impl eframe::App for App {
     fn update(&mut self, egui_ctx: &egui::Context, frame: &mut eframe::Frame) {
         let frame_start = Instant::now();
 
+        if self.startup_options.memory_limit.limit.is_none() {
+            // we only warn about high memory usage if the user hasn't specified a limit
+            self.ram_limit_warner.update();
+        }
+
         if self.icon_status == AppIconStatus::NotSetTryAgain {
             self.icon_status = setup_app_icon();
         }
diff --git a/crates/re_viewer/src/web.rs b/crates/re_viewer/src/web.rs
index 28dfee609af8..eb879b32f3f7 100644
--- a/crates/re_viewer/src/web.rs
+++ b/crates/re_viewer/src/web.rs
@@ -33,7 +33,12 @@ pub async fn start(
         Box::new(move |cc| {
             let build_info = re_build_info::build_info!();
             let app_env = crate::AppEnvironment::Web;
-            let startup_options = crate::StartupOptions::default();
+            let startup_options = crate::StartupOptions {
+                memory_limit: re_memory::MemoryLimit {
+                    // On wasm32 we only have 4GB of memory to play around with.
+                    limit: Some(3_500_000_000),
+                },
+            };
             let re_ui = crate::customize_eframe(cc);
             let url = url.unwrap_or_else(|| get_url(&cc.integration_info));