Bilbasen.dk - Used-car search data extraction

Notes an AI agent reads before it works on bilbasen.dk: what to open, what to call, what breaks. Written by browser-harness contributors after real runs, and kept on GitHub under the MIT license.

Run it in Browser Use Cloud Source on GitHub

Give it to your agent

Any coding agent

Start the task with this line. The Markdown version is the same notes without the page around them.

Read https://browser-use.com/skills/bilbasen.md, then <your task>

Browser Harness

Save the files into your workspace and turn domain skills on. The code below calls its helpers, such as http_get and js. What Browser Harness is.

d="${BH_AGENT_WORKSPACE:-$HOME/.config/browser-harness/agent-workspace}/domain-skills/bilbasen"
mkdir -p "$d" && cd "$d"
curl -sLO https://raw.githubusercontent.com/browser-use/browser-harness/main/agent-workspace/domain-skills/bilbasen/search.md
export BH_DOMAIN_SKILLS=1

Field-tested against www.bilbasen.dk on 2026-09-21 from a logged-out, real Chrome session (CDP). Bilbasen is Denmark's largest used-car marketplace.

Quick summary

Plain HTTP is blocked. http_get / curl with a full Chrome UA returns HTTP 202 with an empty body (JS bot challenge). Use the user's real browser.
Search result pages embed every listing on the page as JSON in <script id="__NEXT_DATA__"> (Next.js SSR). No need to scrape cards or scroll.
Search URL pattern: https://www.bilbasen.dk/brugt/bil/<make>/<model>?pricefrom=<int>&priceto=<int>. Make/model slugs are lowercase (vw, id.4). The site 302s to an internal model id (/brugt/bil/vw/id2314) and appends includeengroscvr=true&includeleasing=false; both URLs work.
30 listings per page; total hits in hits.
This example reads one page. When hits exceeds the listing count, use the visible next-page control.
Wait for listing IDs to change before reading the next page. Remove duplicates by externalId.
Verify the final unique count against hits; report any shortfall instead of claiming complete results.

Extracting listings

import json
new_tab("https://www.bilbasen.dk/brugt/bil/vw/id.4?pricefrom=150000&priceto=195000")
wait_for_load()
raw = js("document.getElementById('__NEXT_DATA__').textContent")
queries = json.loads(raw)["props"]["pageProps"]["dehydratedState"]["queries"]
data = next((q.get("state", {}).get("data") for q in queries
             if isinstance(q.get("state", {}).get("data"), dict)
             and "listings" in q["state"]["data"]), None)
if data is None:
    raise RuntimeError("The page has no listings query")
print(data["hits"], len(data["listings"]))   # e.g. 48, 30

Top-level keys in data: listings, filterOptions, sortOptions, searchRequest, pagination, breadcrumbs, canonicalUrl, hits, totalAbundance.

Fields in each listing

Field	Example	Notes
`externalId`	`6999185`	listing id, also last path segment of `uri`
`uri`	`https://www.bilbasen.dk/brugt/bil/vw/id4/52-pure-5d/6999185`	detail page
`price.price`	`169900`	int DKK, use for math; `price.displayPrice` is formatted
`price.priceType`	`"Retail"`
`make`, `model`	`"VW"`, `"ID.4"`
`variant`	`"77 1ST Pro Performance 5d"`	trim string; use the battery field for capacity
`description`	Danish prose, 800–2900 chars	dealer boilerplate mixed with equipment highlights
`sellerType`	`"Forhandler"` / `"Privat"`	dealer vs private
`saleType`
`location`	object	seller location
`media[]`	`{mediaType: "Picture", url}`	images, `?class=S640X640`
`properties.firstregistrationdate`	`{displayTextShort: "10/2022"}`	month/year of first registration
`properties.mileage`	`"76.500 km"`	Danish thousands separator, parse in code
`properties.hk`	`"148 hk"`	horsepower
`properties.moth`	`"920 kr/år"`	annual ownership tax (ejerafgift)
`properties.trailer`	`"1.000 kg"`	tow rating
`properties.kmt`	`"10,9 sek"`	0–100 acceleration
`properties.electricmotorrange`	`"343 km"`	WLTP range
`properties.batterycapacity`	`"52 kWh batteri"` (`displayTextLong`)
`properties.geartype`	transmission text	gearbox type
`properties.fueltype`	`"El"`	fuel type
`features`	`[]`	empty on search pages; equipment list is not in the search JSON

Each properties.* entry has both displayTextLong and displayTextShort. All numeric values are formatted strings; parse them in code.

Traps

202 empty body from http_get is the bot wall, not a transient error. Do not retry with headers; go through the browser.
features is always empty in search results. Equipment lists must come from the detail page.
Seller descriptions are not spec sheets. Descriptions were seen quoting DC charging speeds that did not match the variant's model year. Verify technical specs against the exact variant and model year. Use properties.batterycapacity for the listed battery capacity.
Danish number formats: 76.500 km is 76,500; 10,9 sek is 10.9.

search.md · updated Oct 9, 2026 · 580 words

Sites change. These notes describe what worked when they were last updated, not a guarantee they still do. If something broke, the fix is a pull request to browser-harness.