Kuberwastaken/claurst · error

No debuggable page found on port

Error message

No debuggable page found on port {}. Make sure Chrome has at least one open tab.

What it means

Thrown by `connect` when querying Chrome's DevTools HTTP endpoint (`/json` list of targets) yields no target of type "page" with a webSocketDebuggerUrl. Chrome is reachable on the debug port but exposes no debuggable page target, so the library cannot obtain a CDP WebSocket URL and aborts the connect.

Solutions

1. Open at least one normal tab in the Chrome instance being debugged.
2. Restart Chrome with --remote-debugging-port=<port> and an initial URL so a page target exists.
3. Verify with `curl http://127.0.0.1:<port>/json` that a target with "type":"page" and webSocketDebuggerUrl appears.
4. Re-run `/chrome connect` after the tab is open.

Example fix

// before: chrome started with no tabs
// http://127.0.0.1:9222/json returns only service workers

// after: start chrome with an initial page
// chrome --remote-debugging-port=9222 https://example.com

let targets: Value = reqwest::get(format!("http://127.0.0.1:{}/json", port)).await?.json().await?;
let ok = targets.as_array().map(|a| a.iter().any(|t| t["type"] == "page" && t.get("webSocketDebuggerUrl").is_some())).unwrap_or(false);
if !ok { /* open a tab or restart Chrome */ }

fn has_page_target(targets: &Value) -> bool {
    targets.as_array().is_some_and(|a| a.iter().any(|t| t["type"] == "page" && t["webSocketDebuggerUrl"].is_string()))
}

match connect(port).await {
    Ok(_) => {},
    Err(e) if e.to_string().contains("No debuggable page") => {
        open_new_tab(port)?;
        connect(port).await?;
    }
    Err(e) => return Err(e),
}

When it happens

Trigger: Chrome runs with --remote-debugging-port but has zero open tabs (all closed, only background/service-worker targets present); the target list JSON has no entry whose `type` equals "page" or whose `webSocketDebuggerUrl` field is absent.

Common situations: Headless Chrome started without an initial URL and all tabs closed; Chrome started with a --remote-debugging-port only reachable in new window modes where no page target exists yet; enterprise Chrome policies hiding debug targets.

Understand the failure class

Background: EmptyResultError / "no results found": when an API or scraper succeeds but returns zero rows — this error's family across 9 libraries.

Related errors

• WebSocket closed unexpectedly
• WebSocket closed by Chrome
• WebSocket connect to
• CDP error
• No screenshot data in response

AI-assisted analysis of Kuberwastaken/claurst@b0637c97ec (2026-09-10). Data as JSON: /api/errors/3baf9ce7103d8c9e. Report an issue: GitHub.

Appendix: source

Thrown at src-rust/crates/commands/src/chrome.rs:129

    /// Connect to Chrome at the given port.
    /// Picks the first available target (tab/page).
    pub async fn connect(port: u16) -> anyhow::Result<String> {
        let http_url = format!("http://localhost:{}/json/list", port);
        let client = reqwest::Client::builder()
            .timeout(std::time::Duration::from_secs(3))
            .build()?;
        let tabs: Value = client.get(&http_url).send().await?.json().await?;

        let ws_url = tabs
            .as_array()
            .and_then(|arr| {
                arr.iter().find(|t| t["type"] == "page").and_then(|t| {
                    t["webSocketDebuggerUrl"].as_str().map(|s| s.to_string())
                })
            })
            .ok_or_else(|| {
                anyhow::anyhow!(
                    "No debuggable page found on port {}. \
                     Make sure Chrome has at least one open tab.",
                    port
                )
            })?;

        let tab_url = tabs
            .as_array()
            .and_then(|arr| {
                arr.iter()
                    .find(|t| t["type"] == "page")
                    .and_then(|t| t["url"].as_str().map(|s| s.to_string()))
            })
            .unwrap_or_default();

        let (ws, _) = connect_async(&ws_url).await.map_err(|e| {
            anyhow::anyhow!("WebSocket connect to {} failed: {}", ws_url, e)
        })?;

View on GitHub (pinned to b0637c97ec)