diff --git a/Cargo.lock b/Cargo.lock
index 29f1114f8789..7b94d35b2529 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -6549,6 +6549,7 @@ dependencies = [
  "nohash-hasher",
  "once_cell",
  "parking_lot",
+ "percent-encoding",
  "rand",
  "re_build_info",
  "re_build_tools",
diff --git a/crates/top/re_sdk/Cargo.toml b/crates/top/re_sdk/Cargo.toml
index a40b1ce15c1d..adc64278d496 100644
--- a/crates/top/re_sdk/Cargo.toml
+++ b/crates/top/re_sdk/Cargo.toml
@@ -68,6 +68,7 @@ itertools.workspace = true
 nohash-hasher.workspace = true
 once_cell.workspace = true
 parking_lot.workspace = true
+percent-encoding.workspace = true
 thiserror.workspace = true
 
 # Optional dependencies
diff --git a/crates/top/re_sdk/src/recording_stream.rs b/crates/top/re_sdk/src/recording_stream.rs
index 1b6fc3a1bfe3..f93e5aa25d62 100644
--- a/crates/top/re_sdk/src/recording_stream.rs
+++ b/crates/top/re_sdk/src/recording_stream.rs
@@ -1738,7 +1738,10 @@ impl RecordingStream {
     /// See [`Self::set_sink`] for more information.
     pub fn connect_grpc(&self) -> RecordingStreamResult<()> {
         self.connect_grpc_opts(
-            format!("http://127.0.0.1:{}", re_grpc_server::DEFAULT_SERVER_PORT),
+            format!(
+                "rerun+http://127.0.0.1:{}",
+                re_grpc_server::DEFAULT_SERVER_PORT
+            ),
             crate::default_flush_timeout(),
         )
     }
diff --git a/crates/top/re_sdk/src/web_viewer.rs b/crates/top/re_sdk/src/web_viewer.rs
index b7b7ac67f924..fb2df732a20a 100644
--- a/crates/top/re_sdk/src/web_viewer.rs
+++ b/crates/top/re_sdk/src/web_viewer.rs
@@ -210,6 +210,12 @@ impl WebViewerConfig {
         };
 
         if let Some(source_url) = source_url {
+            // TODO(jan): remove after we change to `rerun-http`
+            let source_url = source_url.to_string();
+            let source_url = percent_encoding::utf8_percent_encode(
+                &source_url,
+                percent_encoding::NON_ALPHANUMERIC,
+            );
             append_argument(format!("url={source_url}"));
         }
         if let Some(force_graphics) = force_wgpu_backend {
diff --git a/rerun_py/src/python_bridge.rs b/rerun_py/src/python_bridge.rs
index 07b84fa074d7..134cae50f7fa 100644
--- a/rerun_py/src/python_bridge.rs
+++ b/rerun_py/src/python_bridge.rs
@@ -598,13 +598,13 @@ fn connect_grpc(
     };
 
     use re_sdk::external::re_grpc_server::DEFAULT_SERVER_PORT;
+    let url = url.unwrap_or_else(|| format!("rerun+http://127.0.0.1:{DEFAULT_SERVER_PORT}/proxy"));
     let re_uri::RedapUri::Proxy(endpoint) = url
-        .unwrap_or_else(|| format!("rerun+http://127.0.0.1:{DEFAULT_SERVER_PORT}"))
         .parse::<re_uri::RedapUri>()
         .map_err(|err| PyRuntimeError::new_err(err.to_string()))?
     else {
         return Err(PyRuntimeError::new_err(format!(
-            "invalid endpoint, expected {:?}",
+            "invalid endpoint {url:?}, expected {:?}",
             "/proxy"
         )));
     };