Depending on your intent, this term usually refers to one of three things:

Downloading large files in "blocks" or chunks to ensure integrity and speed. 2. Best Practices for Secure Downloading

Your Essential Guide to a "Safe Block Download": Security Tips & Best Practices

What happens if a download isn't safe? The risks range from annoying to catastrophic: Your files are encrypted and held for payment.

Never download software or data blocks from third-party "mirror" sites if an official source exists. Always look for the padlock in your browser and verify the URL. If you are downloading a blockchain, use the official core client (e.g., Bitcoin Core). Verify File Integrity with Hashes

Automatically learns to block invisible trackers. 4. Risks of Unsafe Downloads

Downloading the full ledger (blocks) of a cryptocurrency like Bitcoin or Ethereum safely.

If your goal is to download a tool that performs blocking, security experts generally recommend the following for a safe experience: