Source collection
HammerAlert reads public auction-house calendars and sale listings from more
than 150 houses and marketplaces. Some sources publish structured data; others
require house-specific parsers because the useful information is embedded in
cards, calendar exports, JavaScript payloads, or separate detail pages.
The system keeps the auction-house catalogue as the source of truth for bidding,
registration, condition reports, and final terms. HammerAlert's job is the
planning layer: dates, house, category, region, sale title, source URL, and
enough context to decide whether a sale deserves closer review.
Normalisation and deduplication
Every incoming sale is normalised into a common shape: canonical source name,
title, date range, region, location, category signals, source URL, and stable
HammerAlert detail URL. The normaliser collapses duplicate appearances of the
same sale when a house publishes the same auction through more than one feed or
when a marketplace mirrors a house calendar.
Category pages such as jewellery,
watches, and
modern and contemporary art
use this normalised layer so a collector can compare similar sales across
houses instead of reading each house calendar separately.
Quality controls
Public auction pages are not all treated equally. Thin detail pages stay
reachable for users and crawlers but can be marked noindex,follow
when the source has not published enough sale-specific detail. Richer detail
pages can include source-backed summaries, images, lot counts, viewing dates,
estimate ranges, format labels, and structured data.
The sitemap also uses a quality gate so Google and Bing are pointed first at
stronger hub and detail pages. This is deliberate: a smaller set of useful URLs
is better than asking search engines to evaluate hundreds of near-empty sale
placeholders.
What can drift
Auction calendars change. Houses move dates, add online sessions, merge sale
pages, remove stale announcements, or change website templates. HammerAlert
reruns collectors, normalises fresh data, and keeps operator review tools for
cases where the public page and database no longer match.
If a sale matters commercially, always verify the final catalogue, buyer's
premium, bidding rules, shipping restrictions, and condition information with
the auction house before bidding.