Do travel adapters convert voltage?

No. Almost every popular travel adapter on the market, including all of the picks here, is a plug-shape adapter only and does not convert voltage. High-trust reviewers and the product listings themselves are explicit about this: do not plug a 110V-only hair dryer or curling iron into a 220V outlet through one of these. Use dual-voltage devices (most phone, laptop, and tablet chargers are already 100–240V) or a dedicated voltage converter.