Which sites block cloud browser agents? Benchmark of 23 tasks
In our benchmark, a Claude browser agent in a fresh headless Chromium was blocked on 10 of 23 tasks, in every run of those tasks. On the other 13 tasks it was never marked blocked. Wield's recipes ran in the user's own browser. They passed all runs on 7 of those 10 blocked tasks. Data as of 7 November 2026, from 23 tasks on 21 sites. The benchmark is still running.
Key finding
The browser agent was blocked in every run on these 10 tasks:
- bahn.de (1 of 1 run)
- eventim.de, idealo.de, immobilienscout24.de, lieferando.de, mobile.de, opentable.com, walmart.com, zalando.de and zillow.com (9 of 9 runs each)
The 23 tasks
Each task has 3 fixed queries, and each query runs 3 times per side. "Blocked" is the benchmark's blocked flag. It covers an HTTP 401, 403 or 429 from the site, or the agent reporting a block.
| Site | Task | Browser-agent runs blocked | Agent run passing | Wield passing |
|---|---|---|---|---|
| airbnb.com | search-stays | 0 of 4 | 4 of 4 | 8 of 9 |
| amazon.com | search-products | 0 of 4 | 4 of 4 | 9 of 9 |
| autoscout24.de | search-cars | 0 of 5 | 5 of 5 | 9 of 9 |
| bahn.de | search-connections | 1 of 1 | 0 of 1 | 9 of 9 |
| check24.de | compare-electricity | 0 of 5 | 5 of 5 | 9 of 9 |
| chefkoch.de | search-recipes | 0 of 8 | 8 of 8 | 9 of 9 |
| doctolib.de | get-slots | 0 of 2 | 1 of 2 | 8 of 8 |
| doctolib.de | search-practitioners | 0 of 2 | 2 of 2 | 9 of 9 |
| eventim.de | search-events | 9 of 9 | 0 of 9 | 9 of 9 |
| flixbus.de | search-trips | 0 of 3 | 3 of 3 | 9 of 9 |
| idealo.de | price-lookup | 9 of 9 | 0 of 9 | 9 of 9 |
| immobilienscout24.de | search-rentals | 9 of 9 | 0 of 9 | 0 of 2 |
| jameda.de | get-slots | 0 of 9 | 9 of 9 | 9 of 9 |
| jameda.de | search-doctors | 0 of 9 | 9 of 9 | 9 of 9 |
| kleinanzeigen.de | search-listings | 0 of 2 | 2 of 2 | 9 of 9 |
| lieferando.de | search-restaurants | 9 of 9 | 0 of 9 | 9 of 9 |
| mobile.de | search-cars | 9 of 9 | 0 of 9 | 5 of 9 |
| opentable.com | search-restaurants | 9 of 9 | 0 of 9 | 9 of 9 |
| vinted.de | search-items | 0 of 8 | 7 of 8 | 9 of 9 |
| walmart.com | search-products | 9 of 9 | 0 of 9 | 9 of 9 |
| willhaben.at | search-marketplace | 0 of 4 | 4 of 4 | 9 of 9 |
| zalando.de | search-products | 9 of 9 | 0 of 9 | 0 of 9 |
| zillow.com | search-homes | 9 of 9 | 0 of 9 | 9 of 9 |
How blocks showed up
The blocks had different signals:
- HTTP 403 from the site: bahn.de (on the timetable request), idealo.de (16 requests to the homepage), lieferando.de, mobile.de and zillow.com (9 each on the homepage), and zalando.de (on pages and tracking requests).
- HTTP 401 from the site: immobilienscout24.de (9 requests to the homepage).
- No status in the log: eventim.de, opentable.com and walmart.com. The agent itself reported navigation failures or "site unavailable".
What the blocked sites have in common
Our notes name the protection vendor for most of these sites. Akamai is named for bahn.de, eventim.de, idealo.de, mobile.de and zalando.de. PerimeterX (HUMAN) is named for walmart.com and zillow.com. AWS WAF Bot Control is named for immobilienscout24.de. lieferando.de has Cloudflare in front, and it still returned 403 to the agent. opentable.com has no vendor named in our notes.
Wield was not immune. It passed all runs on 7 of the 10 blocked tasks. It passed 5 of 9 on mobile.de, scored 0 of 2 on immobilienscout24.de, where a check appeared, and 0 of 9 on zalando.de, where the tab was redirected to en.zalando.de. When a check appears, Wield stops and does not solve it.
Method and caveats
- Browser agent: Browser Use 0.13.14 with Claude Sonnet 5.5, stock settings, in a fresh headless Chromium with an empty profile.
- Wield: the recipe ran in an everyday browser (Vivaldi, Chromium 152), with no model in the loop.
- Small samples. Several sides have only 1 to 4 runs. bahn.de has one agent run. The benchmark is paced at about 30 site requests per hour.
- One agent setup. This describes one setup on one date, not every AI agent. A fresh headless browser with an empty profile was blocked. We did not test other setups.
- Chefkoch exception. The log shows HTTP 401 on one API request, but all 8 runs passed and none counts as blocked.
- Scope. The 23 tasks cover 21 sites. The Zalando HTML fallback is excluded because it reuses the main Zalando agent runs.
FAQ
Which sites blocked the browser agent in every run?
In this benchmark: bahn.de (1 run), eventim.de, idealo.de, immobilienscout24.de, lieferando.de, mobile.de, opentable.com, walmart.com, zalando.de and zillow.com (9 runs each).
Does Wield get blocked too?
Sometimes. Wield passed all runs on 7 of the 10 blocked tasks. On the others it passed 5 of 9, 0 of 2 or 0 of 9. Where a site shows a check, Wield stops with site_challenge and the user solves it in their own tab.
Why would a site block a fresh headless browser but not a real one?
Bot-protection systems judge the browser that makes the request. In these runs, the agent's setup was blocked and Wield's requests from a normal browser session were not, on the same sites. We tested one agent setup, so we cannot say which signal caused each block. For a worked example, see the bahn.de benchmark.