The IAB Tech Lab has updated the OpenRTB guidelines to improve transparency and accuracy in web video inventory, better differentiating between in-stream and out-stream placements. These changes address a gray area in the legacy definition of in-stream and help preserve the value of premium, full-focus web video content while clarifying other web video advertising descriptions.

Source: March 2023 Update to OpenRTB is now ready for implementation! – IAB Tech Lab