Price monitoring · Marketplace sellers
Marketplace seller monitoring: featured offer, offer count and shipping per market
On a marketplace the price you track is only half the story; the other half is which seller the page puts in front of the shopper, and who else is waiting behind it. Check each listing on each country site from an exit in that market, so the featured offer, delivery promise and offer count are the ones local shoppers get.
Pay per GB · No subscription · Prices in EUR, excl. VAT
- €0.75
- per GB on ARC Basic, excl. VAT
- −21%
- at 1 TB (€0.59 / GB)
- 185+
- countries, city targeting
- Never
- expires — no subscription
Written for
- Brand channel and distribution managers
- Repricing tool developers
- Marketplace agencies
- MAP and reseller compliance teams
The short answer
- Seller monitoring tracks the featured (buy-button) offer, the full offer list and the delivery terms per listing — a different job from tracking your own price.
- Delivery promises and shipping costs depend on where the marketplace thinks the shopper is; collect each country site from an exit in that country.
- Snapshot the listing and its offer list in one sticky session, so both views describe the same moment and the same location.
- Under EU consumer law, marketplaces must say whether a third-party seller is a trader and explain their main ranking parameters — fields worth storing alongside the offer.
The problem
What goes wrong without the right IPs
You track the price, not the winner
A listing can keep the same lowest price for a week while the featured offer moves between three sellers. If you only store a price, you miss the change your channel team actually needs to act on.
Delivery terms follow the shopper's location
Delivery dates, shipping fees and sometimes whether an offer is shown at all depend on the delivery location the marketplace infers. Collected from the wrong country, the offer list describes a shopper who does not exist.
Listing and offer list disagree
The product page and its "other sellers" view are separate requests. Fetched minutes apart from different exits, they can show different featured sellers and you cannot tell a real change from a collection artefact.
Product pages are heavy
Marketplace product pages carry large scripts, recommendation widgets and images. Per gigabyte, a careless headless browser fetch costs far more than the dozen fields you keep.
Unauthorised sellers surface in one market first
A grey-market reseller often lists in a single country site before spreading. Monitoring only your home marketplace finds them weeks late.
What to collect
What you can collect
- Featured offer seller
- Who wins the buy button now — the single most watched field in seller monitoring.
- Featured offer price and shipping
- The landed price is what the featured-offer decision and the shopper both see.
- Offer count
- How many sellers compete on the listing; a sudden jump often means a new reseller or a price war.
- Full offer list
- Seller name, price, shipping, condition and delivery promise for each offer, not just the winner.
- Fulfilment type
- Marketplace-fulfilled or seller-fulfilled changes delivery speed and, often, the featured-offer outcome.
- Trader status
- In the EU, marketplaces must state whether a third-party seller is a trader; store it with the seller record.
- Delivery promise
- The date range shown to a shopper in that market — a competitive variable in its own right.
- Second displayed offer
- Where a page shows a competing offer next to the featured one, record it; it is the shopper's visible alternative.
How it runs
How a collection run works
- 01
Map listings to markets
For each product, list the identifier on every country site you sell on, and the country you want each one observed from. The same product often has different identifiers per marketplace country.
- 02
Open one sticky session per listing check
Fetch the product page and its offer list in one sticky session of a few minutes, from an exit in that country. Both snapshots then share a location and a moment.
Listing and offer list from one exit14 linesimport uuidimport httpxGATEWAY = "proxy.arcproxies.io:8000"PASSWORD = "PASSWORD"def check_listing(country: str, listing_url: str, offers_url: str) -> tuple[str, str]: sid = uuid.uuid4().hex[:8] user = f"USERNAME_pool-arcfast_country-{country}_session-{sid}_sesstime-5" proxy = f"http://{user}:{PASSWORD}@{GATEWAY}" with httpx.Client(proxy=proxy, timeout=30, follow_redirects=True) as c: listing = c.get(listing_url).text offers = c.get(offers_url).text # same exit, same moment return listing, offers - 03
Parse offers into a row per seller
Store one row per seller per check: seller, price, shipping, condition, fulfilment, delivery promise and whether it was the featured or second displayed offer. Change detection then becomes a query, not a diff of HTML.
- 04
Alert on events, not on prices
Featured-offer changes, new sellers, sellers below your minimum advertised price and offer-count jumps are the events channel teams act on. Price changes alone are noise on a marketplace with active repricers.
- 05
Tune cadence per listing
Hero products in competitive categories may justify several checks a day; the long tail rarely needs more than one. Cadence is your largest cost lever on per-GB billing.
Setup
Recommended setup
Marketplace pages are stricter than most catalogue sites and depend on the shopper's market, so residential is the default here and ISP is the saving where it works.
| Plan | Role | Session | Targeting | Price |
|---|---|---|---|---|
ARC Fast Rotating residential | Default for listing and offer checks Residential exits in the market of each country site, held for the listing and offer-list fetch so both show the same featured seller. | Sticky, 5 minutes per listing | Country | €2.00 / GB €1.12 at 1 TB (−44%) |
ARC Ultra Premium residential | For the marketplaces that matter most Premium residential for the country sites where ARC Fast leaves you with failures you cannot otherwise explain. Route only those there. | Sticky, 5 minutes per listing | Country | €3.50 / GB €2.17 at 1 TB (−38%) |
ARC Basic Rotating ISP | For seller storefronts and static pages Seller profile pages and policy pages change rarely and are light. Collect them on the cheapest pool. | Rotating | Country | €0.75 / GB €0.59 at 1 TB (−21%) |
Prices are list prices in EUR, excl. VAT. Volume discounts apply automatically at checkout — full ladder on the pricing page.
Connect
One connection string per market
The country, city and sticky session are tokens in the username. Change the token, change the market; keep the session handle, keep the IP.
http://USERNAME_pool-arcfast_country-de_session-k3f9a1x2_sesstime-10:PASSWORD@proxy.arcproxies.io:8000Swap _country-de for any market you quote. The full grammar is on the residential proxies page.
Illustration
What daily seller checks on 2,000 listings costs
An illustration with round numbers — your pages, payloads and retry rate will differ. The arithmetic is the real price ladder.
Assumptions
- Products monitored
- 2,000
- Marketplace country sites
- 4
- Pages per check
- 2 (listing + offer list)
- Cadence
- once a day
- Weight per page, images blocked
- 500 KB
- Bandwidth per month
- ≈ 240 GB
On ARC Fast
€326.40per month, excl. VAT
240 GB bought in one purchase at €1.36 / GB (−32% volume rung, applied automatically).
The same 240 GB on ARC Ultra: €621.60 at €2.59 / GB. Route only the jobs that need it through the pricier pool.
Checking your 200 most contested products four times a day instead of once adds roughly another 72 GB a month at the same page weight. Running a full browser with images loaded can multiply the per-page weight several times.
Bandwidth never expires, so a bigger single purchase is only ever cheaper per GB. See the ladder.
In depth
Marketplace sellers, in depth
Seller monitoring is not price monitoring
Price monitoring asks "what does this product cost?". Seller monitoring asks "who is selling it, on what terms, and who is the marketplace putting first?". The second question needs the whole offer list, every time, and it needs it from the shopper's market.
The difference shows up in what you alert on. A repricer cares about the featured offer's landed price; a brand's channel team cares that an unknown seller appeared in Italy; a compliance team cares that an authorised reseller is advertising below the agreed minimum.
| Question | Fields you need | Who asks it |
|---|---|---|
| Who holds the featured offer? | Featured seller, landed price, fulfilment type | Repricers, brands |
| Who else is selling? | Full offer list, offer count, trader status | Brand protection, channel managers |
| Are resellers sticking to terms? | Seller, price per offer, timestamp | MAP and distribution compliance |
| How does delivery compare per market? | Delivery promise and shipping per offer, per country site | Marketplace agencies, operations |
How the featured offer is chosen, and what regulators have said about it
Marketplaces do not publish the full algorithm that picks the featured offer, but they are no longer silent about it. In the EU, the Omnibus Directive requires online marketplaces to give general information on the main parameters that determine the ranking of offers shown for a search, and their relative importance, in a section directly reachable from the results page. They must also say whether the third party offering a product is a trader, based on that party's declaration.
Competition law has looked at the featured offer directly. In December 2022 the European Commission made commitments by Amazon legally binding: to treat all sellers equally when ranking offers for its Buy Box, and to display a second competing offer where one from a different seller is sufficiently differentiated on price or delivery. The Buy Box and Prime commitments run for seven years and cover its marketplaces in the European Economic Area except Italy.
For a monitoring team the practical consequence is simple: on EEA listings, record the second displayed offer as well as the winner, and store the trader-status label. Both are visible on the public page and both are part of what a shopper sees.
Why the exit country changes the offer list
A marketplace has to decide which offers it can deliver to the shopper and how fast. Without a signed-in delivery address, it infers the location — and the delivery promise, shipping fee and sometimes the eligible offers follow from that inference.
So the country of the exit is part of the measurement. Collect the German site from a German exit and the French site from a French one, and the delivery terms you store are those a local shopper is shown. Where a marketplace lets a logged-out visitor set a delivery postcode, use that for finer precision; our city targeting covers a fixed list of metros, not postcodes.
- Featured offer — can differ by market when sellers ship to some countries and not others.
- Shipping and delivery date — almost always location-dependent.
- Offer count — sellers who do not ship to the inferred location may drop out of the list.
Keeping the check light
- Prefer HTML over a browser where the offer list is in the server-rendered page; a headless browser is the exception, not the default.
- Block images and third-party scripts — a marketplace product page without them is a fraction of its full weight.
- Fetch the offer list only when it can have changed — for example when the offer count on the listing differs from the last check.
- Pace each country site and back off on rate-limit responses; see handling 429 rate limits.
The bandwidth guide has measured page weights to plan against; sibling page grocery price monitoring covers the store-level version of the same problem.
Works with anything that takes a proxy URL
- Python requests / httpx
- Node.js
Playwright- Scrapy
Crawlee- Docker
FAQ
Questions
Something not covered? Write to contact@arcproxies.io.
What is marketplace seller monitoring?
It is tracking, per listing and per marketplace country site, which seller holds the featured offer, how many other sellers compete, and the price, shipping, fulfilment and delivery promise of each offer. It differs from price monitoring because the seller and the terms matter as much as the price.
Why do I need an exit in each marketplace country?
Because delivery promises, shipping fees and sometimes which offers are shown depend on where the marketplace thinks the shopper is. Collecting each country site from an exit in that country means the offer list you store is the one local shoppers see.
Should the listing and the offer list use the same IP?
Yes. Fetch both in one sticky session so they share a location and a moment. Fetched from two different exits minutes apart, they can show different featured sellers, and you cannot tell a real change from a collection artefact.
Which plan should I use for marketplace monitoring?
ARC Fast is the default: residential exits with country targeting and sticky sessions. Route the specific marketplaces where you see unexplained failures to ARC Ultra, and collect light seller storefront and policy pages on ARC Basic.
How much bandwidth does daily seller monitoring use?
With images blocked and around 500 KB per page, checking 2,000 products on four country sites once a day, listing plus offer list, is about 240 GB a month. Cadence is the biggest lever: check contested products often and the long tail rarely.
Can I monitor offers that are only visible when signed in?
No. Monitoring here means the public, logged-out listing and offer pages. Anything that needs a seller or customer account is outside what our acceptable use policy supports.
Sources & review
Last reviewed by the ARC Proxies team. Prices are read from the live catalog at build time.
- [1]European Commission: Antitrust: Commission accepts commitments by Amazon barring it from using marketplace seller data, and ensuring equal access to Buy Box and Prime (IP/22/7777)
- [2]EUR-Lex: Directive (EU) 2019/2161 (Omnibus Directive), Articles 3 and 4: ranking transparency and trader status on online marketplaces
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