Semrush

Semrush is a large marketing suite mainly known for SEO, but its advertising research is widely used by PPC managers. Enter a competitor's domain and it shows the paid keywords it has seen them bid on, examples of their ad copy, and an estimate of their traffic and spend.

These figures come from Semrush's own data collection, not from Google, so treat them as estimates and patterns rather than exact numbers. They are useful for spotting which keywords competitors keep paying for over months, how they word offers, and which landing pages they send traffic to.

The suite also includes keyword research with cost per click data, which helps when planning a new campaign or market. Full access requires a paid plan; a limited free account lets you try a few lookups.