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Respect Server Rate Limits When Downloading Images — Bulk Image Downloader Pro

danito

Fifty parallel requests to a small host is a fast way to get throttled. HTTP 403 responses, timeouts, and half-finished batches are usually the server asking you to slow down. To respect server rate limits when downloading images, space out scraping, cap parallel downloads, and split large jobs into manageable tasks.

Bulk Image Downloader Pro exposes delay, concurrency, queue, and schedule controls on the options page. The extension cannot override a host that has already blocked your IP—you have to wait or reduce load and try again later.

Step 1: recognize when you are hitting a limit

Symptoms include sudden 403 or 429 errors mid-batch, downloads that stall at the same host, and scrape pages that stop returning images even though the site loads fine in a normal tab. If errors cluster on one domain, treat it as a pacing problem before you blame the URL list.

Step 2: slow down bulk URL scraping

When the side-panel scraper walks a list of page URLs, the request delay setting spaces each page load. The minimum delay is 500 ms; many operators use one to three seconds on smaller sites. Pair delay with the max-URL cap (up to 500 URLs per bulk scrape) so one run does not hammer a host with hundreds of page fetches. Split oversized jobs into several tasks with smaller URL lists.

Step 3: tune parallel download concurrency

The global max parallel downloads setting controls how many image files transfer at once. Licensed PRO allows up to 100 parallel downloads; Try PRO is capped at 1; the Basic download-only tier caps at 2. Start conservatively on unfamiliar hosts—five to ten parallel downloads—and raise the count only if errors stay low. If a site starts failing, lower concurrency before you retry the whole batch.

Per-task Respect order downloads files sequentially in URL list order. It is slower than parallel mode but gentler on hosts that dislike concurrent hits from the same client.

Step 4: queue tasks instead of launching everything at once

Enable Queued Download on the options page so pending tasks run one after another instead of all starting together. That smooths traffic when you have several large batches ready. For work that can wait, schedule individual tasks at least two minutes ahead—scheduled runs need Chrome open; there is no background server that runs downloads while the browser is closed.

Step 5: combine pacing with stable packaging

For very large sets, enable per-task ZIP mode so hundreds of files become one archive. ZIP does not replace polite request timing, but it reduces browser download-event pressure when you also run higher parallel counts on Licensed PRO.

What the tool cannot fix

  • hard IP or account blocks that require waiting hours or contacting the site owner
  • guaranteed automatic retry with exponential backoff on every failed request
  • downloads while Chrome is fully closed

Polite pacing is faster in the long run than restarting failed batches.

Install Bulk Image Downloader Pro when bulk runs should finish cleanly instead of tripping host defenses.

Continue reading: Export Image URLs to Spreadsheet.

Get Bulk Image Downloader Pro on the Chrome Web Store, watch the tutorial video, or visit our YouTube channel for more rate-limit workflow tips.