Compare Two Scraper Sessions and Export the JSON

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Knowing what changed between two scrapes

Saving sessions is useful on its own, but the real payoff shows up when you scrape the same source twice. Galleries get updated. Boards gain new pins. A listing page rotates its photos. The question you actually care about is rarely “what is on this page” — it is “what is different from last time.” Eyeballing two long URL lists to answer that is slow and error-prone.

Bulk Image Downloader From URL List handles this with Compare Sessions, built right into the side panel scraper alongside your saved session history.

Running a session comparison

From the Sessions area, choose Compare Sessions, pick two saved sessions, and run the diff. The extension lines up the two image lists and sorts every URL into three buckets:

  • Added — URLs present in the newer session but not the older one. These are the fresh images.
  • Removed — URLs that were in the earlier session but are gone now.
  • Common — URLs that appear in both, the unchanged overlap.

That breakdown turns a vague “something changed” into a precise answer. If you are tracking a board or a product gallery over time, the Added list is often all you need to grab the new material without re-downloading everything you already have.

Export and import session JSON

Sessions are not locked inside one browser. Export Session writes the session out as a JSON file, images included, so you can keep a backup or hand it to a teammate. On the other side, Import Session loads that JSON back into the scraper, dropping the session into your history so you can resume or compare it like any other.

This export/import pair is what makes the comparison feature genuinely portable. A few practical uses:

  • Backups — archive an important pull as a file so it survives a reinstall or a cleared profile.
  • Sharing — send a session to a colleague who can import it and see the exact same results.
  • Versioning — keep dated exports of the same source, then import any two and diff them later.

Putting it to work

A reliable routine looks like this: scrape a source today and save the session, scrape it again next week and save that too, then run Compare Sessions on the pair. Read the Added bucket to capture only what is new, glance at Removed to catch anything that disappeared, and export whichever sessions you want to keep as JSON for safekeeping.

Everything here is client-side, so your sessions and exports stay on your machine unless you choose to share them. That makes comparison a low-friction habit — one diff tells you what moved, and a single export keeps the evidence. For teams tracking changing image sources, it is a far cleaner answer than re-scraping blind every time.