Cross-Origin Read Blocking (CORB)

Cross-Origin Read Blocking (CORB) is an algorithm that can identify and block dubious cross-origin resource loads in web browsers before they reach the web page. CORB reduces the risk of leaking sensitive data by keeping it further from cross-origin web pages. In most browsers, it keeps such data out of untrusted script execution contexts. In browsers with Site Isolation, it can keep such data out of untrusted renderer processes entirely, helping even against side channel attacks like Spectre.


Many of the effects of CORB are not observable since the responses it blocks tend to be opaque to web pages in the first place. However, there are 4 observable changes to the web platform to make CORB possible, as outlined in the Blink Intent here: Web developers can learn more about how CORB affects their sites at




Working draft or equivalent

Status in Chromium


Enabled by default (tracking bug) in:

  • Chrome for desktop release 67
  • Chrome for Android release 68
  • Android WebView release 68
  • Opera release 54
  • Opera for Android release 54

Consensus & Standardization

After a feature ships in Chrome, the values listed here are not guaranteed to be up to date.


Last updated on 2018-06-01