Devtools network performance timing

  • Queueing. The browser queues requests when:
    • There are higher priority requests.
    • There are already six TCP connections open for this origin, which is the limit. Applies to HTTP/1.0 and HTTP/1.1 only.
    • The browser is briefly allocating space in the disk cache
  • Stalled. The request could be stalled for any of the reasons described in Queueing.
  • DNS Lookup. The browser is resolving the request's IP address.
  • Proxy negotiation. The browser is negotiating the request with a proxy server.
  • Request sent. The request is being sent.
  • ServiceWorker Preparation. The browser is starting up the service worker.
  • Request to ServiceWorker. The request is being sent to the service worker.
  • Waiting (TTFB). The browser is waiting for the first byte of a response. TTFB stands for Time To First Byte. This timing includes 1 round trip of latency and the time the server took to prepare the response.
  • Content Download. The browser is receiving the response.
  • Receiving Push. The browser is receiving data for this response via HTTP/2 Server Push.
  • Reading Push. The browser is reading the local data previously received.

Time spent in a queue waiting for a network connection.
DNS resolution
Time taken to resolve a host name.
Time taken to create a TCP connection.
Time taken to send the HTTP request to the server.
Waiting for a response from the server.
Time taken to read the entire response from the server (or cache).