Compatibility evidence you can inspect.
This example uses Flex and gap. Select your target clients and inspect the recorded support, conditions and source dates. Free preview uses synthetic HTML and saves nothing.
Target email clients
Choose the clients your customers use. See source findings, recorded versions and test dates for 8 CSS features. Check actual layouts separately, including fallbacks and conditional Outlook code.
The strict gate also blocks partial/conditional/unknown findings, external styles, conditional comments and dynamic values. Unmapped declarations remain outside this catalog, even in strict mode. Removing all clients disables the saved compatibility check.