> ## Documentation Index > Fetch the complete documentation index at: https://docs.apostate.dev/llms.txt > Use this file to discover all available pages before exploring further. # Ad verification > Open an ad link as visitors in several regions and on several desktops, and record the redirect chain, the landing page and a screenshot for each. You run or verify ad campaigns and need to see which landing page a visitor in a given region on a given desktop reaches, and through which redirects. This walkthrough opens an ad link once per region and persona, prints every main-frame response on the way and saves a screenshot of the page it ends on. Opening a tracking link can register a click with the ad network. Check links from campaigns you run or are engaged to verify. ## What Apostate changes A [persona](/concepts/personas) is the platform a launch presents. It sets the operating system in the `User-Agent`, the Client Hints and `navigator.platform`, which ad servers and landing pages use to pick a creative or a download page. Personas are Windows, macOS and Linux desktops. Apostate has no mobile personas. A proxy gives the visit an IP address in the region. Before launch, the package sets the locale and timezone from the proxy's exit, so the language and timezone agree with the IP address. ## Set up ```bash theme={null} pip install apostate apostate install apostate fonts install windows git clone https://github.com/heretic-tech/apostate.git cd apostate/examples/use-cases/ad-verification ``` `apostate fonts install windows` is for Linux and macOS hosts ([Fonts](/guides/fonts)). [`verify_ads.py`](https://github.com/heretic-tech/apostate/blob/main/examples/use-cases/ad-verification/verify_ads.py) takes an ad or tracking link. For each region, it reads a proxy from `APOSTATE_PROXY_US`, `APOSTATE_PROXY_DE` or `APOSTATE_PROXY_FR` and skips a region whose variable is not set. With no link, it runs against a local ad server. The server redirects `/click` to `/track`, and `/track` to a landing page in the language of `Accept-Language`. The landing page's script sends Mac visitors on to a `/mac` page. ## The script `follow()` opens the link with one persona and records each response to a main-frame navigation. That covers HTTP redirects and navigations a page's script starts: ```python theme={null} def follow(url, persona, options, screenshot): """Open url and return the main-frame responses in order, the final URL and the page's region.""" chain = [] with launch(fingerprint=42, fingerprint_platform=persona, **options) as browser: page = browser.new_page() page.on("response", lambda response: chain.append((response.status, response.url)) if response.request.is_navigation_request() and response.frame == page.main_frame else None) page.goto(url) page.wait_for_load_state("networkidle") region = page.evaluate("[Intl.DateTimeFormat().resolvedOptions().timeZone, navigator.language]") page.screenshot(path=screenshot, full_page=True) return chain, page.url, region ``` Each region's launch options come from its proxy. In the local demo, a region is only its locale and timezone: ```python theme={null} for region, locale, timezone, variable in REGIONS: proxy = os.environ.get(variable) if server is not None: # The local demo has no proxies, so each region is its locale and timezone. options = {"locale": locale, "timezone": timezone, "geoip": False} elif proxy: # Through a proxy the package sets locale and timezone from the exit. options = {"proxy": proxy} else: print(f"{region} skipped: {variable} is not set") continue ``` ## Run the demo ```bash theme={null} python3 verify_ads.py ``` ```text theme={null} US windows America/New_York en-US 302 http://127.0.0.1:8766/click?campaign=spring 302 http://127.0.0.1:8766/track?campaign=spring 200 http://127.0.0.1:8766/landing/en?campaign=spring final http://127.0.0.1:8766/landing/en?campaign=spring screenshot out/US-windows.png US macos America/New_York en-US 302 http://127.0.0.1:8766/click?campaign=spring 302 http://127.0.0.1:8766/track?campaign=spring 200 http://127.0.0.1:8766/landing/en?campaign=spring 200 http://127.0.0.1:8766/landing/en/mac?campaign=spring final http://127.0.0.1:8766/landing/en/mac?campaign=spring screenshot out/US-macos.png DE windows Europe/Berlin de-DE 302 http://127.0.0.1:8766/click?campaign=spring 302 http://127.0.0.1:8766/track?campaign=spring 200 http://127.0.0.1:8766/landing/de?campaign=spring final http://127.0.0.1:8766/landing/de?campaign=spring screenshot out/DE-windows.png DE macos Europe/Berlin de-DE 302 http://127.0.0.1:8766/click?campaign=spring 302 http://127.0.0.1:8766/track?campaign=spring 200 http://127.0.0.1:8766/landing/de?campaign=spring 200 http://127.0.0.1:8766/landing/de/mac?campaign=spring final http://127.0.0.1:8766/landing/de/mac?campaign=spring screenshot out/DE-macos.png FR windows Europe/Paris fr-FR 302 http://127.0.0.1:8766/click?campaign=spring 302 http://127.0.0.1:8766/track?campaign=spring 200 http://127.0.0.1:8766/landing/fr?campaign=spring final http://127.0.0.1:8766/landing/fr?campaign=spring screenshot out/FR-windows.png FR macos Europe/Paris fr-FR 302 http://127.0.0.1:8766/click?campaign=spring 302 http://127.0.0.1:8766/track?campaign=spring 200 http://127.0.0.1:8766/landing/fr?campaign=spring 200 http://127.0.0.1:8766/landing/fr/mac?campaign=spring final http://127.0.0.1:8766/landing/fr/mac?campaign=spring screenshot out/FR-macos.png ``` The first line of each block is the region, the persona, and the timezone and language the landing page read. The two `302` lines are the HTTP redirects. The tracker chose the landing page from `Accept-Language`. Under the macOS persona, the landing page's script moved on to `/mac`, which shows as a second `200`. ## Run through regional proxies Set a proxy for each region you want to check, then pass the link: ```bash theme={null} export APOSTATE_PROXY_US="socks5://user:pass@proxy.example:1080" export APOSTATE_PROXY_DE="socks5://user:pass@proxy.example:1081" python3 verify_ads.py "https://ads.example/click?id=123" ``` The script skips a region with no proxy. With no variable set, the output is: ```text theme={null} US skipped: APOSTATE_PROXY_US is not set DE skipped: APOSTATE_PROXY_DE is not set FR skipped: APOSTATE_PROXY_FR is not set ``` Through a proxy, the package looks up the exit's location before launch, so the timezone and language on each block's first line are the ones it found. Check that they belong to the region. If the lookup fails, the package prints a warning that starts with `apostate: `, and the persona uses `en-US` and the host's timezone. From 0.4.4 the warning is also in `browser.apostate_diagnostics["warnings"]`. [Proxies](/guides/proxies#geoip-through-the-proxy) covers the lookup. ## Points for this job * **Proxies.** Use one exit per region, sticky for the length of a launch. [Proxies](/guides/proxies#sticky-and-rotating-exits) covers sticky sessions. * **Seeds.** Each persona uses [seed](/concepts/seeds-and-identity) 42, so a rerun visits with the same two machines and a change in the result comes from the campaign. To see how a campaign treats other machines of one persona, add seeds. * **What the chain records.** The chain holds HTTP redirects and the navigations a page's script starts, such as `location.replace()`. An ad inside an iframe navigates its own frame, so filter on that frame instead of `page.main_frame`. `wait_for_load_state("networkidle")` returns after 500 ms with no network connections. The chain misses a redirect that a page schedules later than that. To catch it, add `page.wait_for_timeout()` before the screenshot. * **Headless.** The screenshots are full-page captures from a headless launch, which presents the persona's screen and window.