diff --git a/README.md b/README.md
index bd5f48e..5a12971 100644
--- a/README.md
+++ b/README.md
@@ -232,6 +232,12 @@ is JSON); `tags` always holds at least `version`, and
 `install` whenever the client has an [installation ID](#every-event-carries-a-random-server-id). The server assigns the
 timestamp. A `201` is success; anything else is logged at `FINE` and dropped.
 
+Redirects are not followed. The body is streamed with a fixed length, so
+`HttpURLConnection` cannot re-send it to a redirect target: a redirect is
+logged at `FINE` and the report is dropped, like any other answer that is
+not `201`. Give `baseUrl` as the final URL — `https://` if the server
+redirects `http://` there — or nothing reaches the server.
+
 ## Keys
 
 A key identifies the program to the server and lets the operator revoke it;
diff --git a/src/main/java/software/stephenson/trace/TraceClient.java b/src/main/java/software/stephenson/trace/TraceClient.java
index c83a2b9..6a56831 100644
--- a/src/main/java/software/stephenson/trace/TraceClient.java
+++ b/src/main/java/software/stephenson/trace/TraceClient.java
@@ -243,7 +243,10 @@ private TraceClient(Builder builder) {
      * at {@code version}, reporting to the trace server at {@code baseUrl}.
      * The version is sent as the tag {@code version} on every event; a blank
      * one, or one longer than {@value #MAX_TAG_LENGTH} characters, is an
-     * {@link IllegalArgumentException}.
+     * {@link IllegalArgumentException}. Redirects are not followed, so
+     * {@code baseUrl} must be the final URL (e.g. {@code https://} when the
+     * server redirects {@code http://} there); otherwise every report is
+     * dropped and logged at {@code FINE}.
      */
     public static Builder builder(String baseUrl, String application, String version) {
         return new Builder(baseUrl, application, version);