Know the marginbefore the hammer.
PreHammer overlays the listing you're already on: live comps, MOT history, auction premium and a BUY or PASS before you bid.
No card · BCA, Manheim, Copart, AutoTrader, eBay, Gumtree, Marketplace
What you see on every listing
Ford Focus ST-Line · 2021 · 38,400 mi
Ask £12,995 · Grade 2 · 1.5 EcoBoost
Retail (live UK comps)
£13,500 – £15,200 · mid £14,300
Margin
| Buy + premium + prep | £13,295 |
| Realistic sell | £14,200 |
| Profit | +£905 |
How it works
Three steps. Same on every site.
No dashboard to learn. It lives on the tab you already have open.
1
Install the extension
Chrome Web Store. Paste your API key from the welcome email. Five full appraisals free, no card.
2
Open any listing
BCA, Manheim, Copart, AutoTrader, eBay, Gumtree or Marketplace. Click the PreHammer button on the page you are already on.
3
Read the sheet
Live comps, MOT trail, margin table and a BUY, PASS or DEPENDS before you bid or message the seller.
The appraisal sheet
Everything you'd scribble on a notepad
One click. Same sections whether you're on an auction lot or a retail ad.
Verdict
BUY, PASS or DEPENDS, first
Not a wall of data. A straight call on whether the lot is worth your hammer, with the reasons underneath.
Retail comps
UK retail comps pulled now
Median and price band for that make, model and year, fetched when you click from live UK listing data, not a stale guide.
DVLA + MOT
Plate check and MOT history
Make, fuel, tax status and recorded mileage from MOT tests. Listing says 67k but MOT says 94k? Flagged in red before you bid.
Margin table
Hammer to forecourt maths
Buy price, buyer's premium on auctions, prep, selling costs and a realistic ask. One profit number at the bottom.
Known faults
Expensive surprises, upfront
Model-specific fault list with typical UK repair bands and eBay parts links. DSG, timing belt, EGR, the usual killers.
Pass early. Bid with a number.
Real decisions the sheet is built for.
Vauxhall Corsa 1.2 · 2019 · 67,200 mi
Auction · Grade 3
MOT trail shows 94,100 mi at last test. Listing under-reported mileage. Retail mid £7,200. Walk.
Ford Focus ST-Line · 2021 · 38,400 mi
Auction · Grade 2
Clean MOT, no clocking flags. Retail mid £14,300 after premium and prep. Est. +£905 margin.
One flip pays for the year
5 free full appraisals to start. Pick a plan when you're buying regularly.
Free trial
5 full appraisals · any listing · no card
- ▪Full sheet on any listing
- ▪Live UK retail comps
- ▪DVLA, MOT & clocking check
Ex VAT · Cancel anytime via Stripe
FAQ
What counts as a scan?+
One full appraisal, one scan. Re-opening the same listing uses cache and doesn't count. Allowance resets on the 1st of each month.
Does the profit table change for auction lots?+
Yes. On BCA, Manheim and Copart we add buyer's premium and adjust sell-side estimates for auction-bought stock.
How fresh are the retail comps?+
Pulled when you click from live UK sold and active listing data matched to make, model, year and mileage, not a printed price guide.
What if there's no reg plate on the listing?+
Margin and comps still run from the ad text. DVLA/MOT sections stay empty and the verdict flags what's unverified.
Any setup beyond installing the extension?+
Paste your API key from the welcome email. We host DVLA, MOT and comp lookups. You don't configure data feeds.
Can I cancel any time?+
Yes. Open the billing portal at prehammer.com/billing with your checkout email. Access continues until the end of your billing period.
Lost your subscription key?+
Open Account in the footer and sign in with your checkout email. You can copy your key there anytime. If you cannot sign in, use Recover key (email plus last 4 characters of your key).
Run it on your next lot
Install, open a listing, hit appraise. You'll know if the margin works before you bid.
Chrome Web Store →