arduino/Arduino · error · IOException

Too many redirect {requestURL}

Error message

Too many redirect {requestURL}

What it means

Thrown by the private recursive makeConnection when a URL request exceeds the allowed redirect-following limit (movedTimes). HttpConnectionManager follows HTTP 3xx Location redirects up to a fixed cap; if the server keeps responding with redirects past that cap (redirect loop, auth bounce, etc.), this fires with the original requestURL. It means the target URL never yielded a direct response — fix the URL or the server's redirect behavior.

Source

Thrown at arduino-core/src/cc/arduino/utils/network/HttpConnectionManager.java:109

  }

  public HttpURLConnection makeConnection(Consumer<HttpURLConnection> beforeConnection)
    throws IOException, NoSuchMethodException, ScriptException, URISyntaxException {
    return makeConnection(this.requestURL, 0, beforeConnection);
  }


  public HttpURLConnection makeConnection()
    throws IOException, NoSuchMethodException, ScriptException, URISyntaxException {
    return makeConnection(this.requestURL, 0, (c) -> {
    });
  }

  private HttpURLConnection makeConnection(URL requestURL, int movedTimes,
                                           Consumer<HttpURLConnection> beforeConnection) throws IOException, URISyntaxException, ScriptException, NoSuchMethodException {
    if (movedTimes > maxRedirectNumber) {
      throw new IOException("Too many redirect " + requestURL);
    }

    Proxy proxy = new CustomProxySelector(PreferencesData.getMap()).getProxyFor(requestURL.toURI());

    final String requestId = UUID.randomUUID().toString().toUpperCase().replace("-", "").substring(0, 16);
    HttpURLConnection connection = (HttpURLConnection) requestURL.openConnection(proxy);

    // see https://github.com/arduino/Arduino/issues/10264
    // Workaround for https://bugs.openjdk.java.net/browse/JDK-8163921
    connection.setRequestProperty("Accept", "*/*");

    connection.setRequestProperty("User-agent", userAgent);
    connection.setRequestProperty("X-Request-ID", requestId);
    if (id != null) {
      connection.setRequestProperty("X-ID", id);
    }
    if (requestURL.getUserInfo() != null) {
      String auth = "Basic " + new String(

View on GitHub (pinned to a0df6e0e83)

Solutions

1. Verify the final URL resolves correctly (curl -IL <url>) and fix server-side redirect loops
2. Remove one hop by using the final destination URL directly
3. Increase maxRedirectNumber if the chain is legitimately long
4. Bypass or fix the proxy that is injecting redirects

Example fix

// before
HttpURLConnection c = new HttpConnectionManager(url).makeConnection(consumer);
// after: use the resolved final URL
HttpURLConnection head = (HttpURLConnection) url.openConnection();
head.setInstanceFollowRedirects(false);
String loc = head.getHeaderField("Location");
URL finalUrl = (loc != null) ? new URL(loc) : url;
HttpURLConnection c = new HttpConnectionManager(finalUrl).makeConnection(consumer);

HttpURLConnection c = (HttpURLConnection) url.openConnection();
c.setInstanceFollowRedirects(false);
if (c.getResponseCode() >= 300 && c.getResponseCode() < 400) {
  String loc = c.getHeaderField("Location");
  if (loc != null && new URL(loc).equals(url)) throw new IllegalStateException("Redirect loop");
}

try {
  connection = new HttpConnectionManager(url).makeConnection(before);
} catch (IOException e) {
  if (e.getMessage().startsWith("Too many redirect")) {
    throw new IllegalStateException("Resolve redirect loop for " + url, e);
  } else throw e;
}

When it happens

Trigger: makeConnection() recursively follows 3xx Location headers; movedTimes exceeds maxRedirectNumber for requestURL, commonly a redirect loop or a redirect chain longer than the configured limit.

Common situations: Server redirect loop (http->https misconfig, login loops); a redirect chain of 5+ hops; a misbehaving proxy rewriting Location headers; URL pointing to a captive portal.

Related errors

• Exceeded %s redirects.
• Error downloading {0}
• Unable to fetch PAC file at {pac}. Response code is {respons
• Received invalid http status code from server: {resp}
• Received response with content-encoding: %s, but failed to d

AI-assisted analysis of arduino/Arduino@a0df6e0e83 (2026-09-06). Data as JSON: /api/errors/fe31648abb94b7c5. Report an issue: GitHub.