ReadLayer is a free Chrome add-on that automatically highlights similar keywords or phrases on the web or PDFs. With ReadLayer, you can find information faster while you browse, making it easier to locate relevant content.

The free version of ReadLayer offers a comprehensive set of features, including regular expressions (Regex) and the ability to find similar terms. It also allows you to highlight only terms that are in proximity to other terms, providing more precise search results. ReadLayer provides a highlights summary, allowing you to navigate across the highlighted terms. You can also add items to themes and activate or deactivate themes depending on your current research.

Additionally, ReadLayer supports dynamic sites, ensuring that highlights auto-refresh on content changes. It works in SVG text and supports multiple languages. You can import/export your entire collection of terms and export the highlights for easy processing. ReadLayer also offers domain whitelisting/blacklisting, allowing you to automatically highlight only the sites you want.

For those looking for more advanced features, ReadLayer Premium is available. It includes multi-highlighting in PDFs directly in your browser.