You can use **Woboq** online code browser available [here](https://clickhouse-test-reports.s3.yandex.net/codebrowser/html_report///ClickHouse/dbms/src/index.html). It provides code navigation and semantic highlighting, search and indexing. The code snapshot is updated daily.
Also you can browse sources on [GitHub](https://github.com/ClickHouse/ClickHouse) as usual.
If you're interested what IDE to use, we recommend CLion, QT Creator, VS Code and KDevelop (with caveats). You can use any favourite IDE. Vim and Emacs also count.