Chrome's built-in downloads work fine for small files, but they can struggle with large downloads over an unstable connection, since a dropped connection often means starting over. A dedicated download manager extension takes over the job, breaking files into chunks, resuming failed downloads and giving you more control over where files land.
Why use a download manager over Chrome's built-in downloads
Chrome downloads files sequentially and cannot resume most downloads after a connection drop or browser restart. A download manager extension can split a large file into segments downloaded in parallel, which often speeds up the transfer, and can resume from where it stopped instead of restarting.
Internet Download Manager vs Chrome extensions
Internet Download Manager, often called IDM, is a separate Windows application that integrates with Chrome through its own extension to catch downloads from the browser. If you already use IDM, install its official companion extension rather than an unrelated one claiming similar features, and confirm compatibility with your Chrome version.
What to check before installing a download manager extension
Download manager extensions need permission to read your downloads and sometimes to access websites so they can detect downloadable files. Prefer extensions that are actively updated, explain their permissions clearly, and let you disable automatic file interception if you only want it for specific downloads.