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Set a custom User-Agent using the parameter or option your screenshot provider documents; there is no universal field name or request format. For example, Screenshot APIs accepts a user_agent field in a POST JSON body, ScreenshotCenter documents a user_agent query parameter, and the command-line tool shot-scraper uses --user-agent.
Choose the format your screenshot tool expects
A User-Agent is sent with an HTTP request to identify the client. Screenshot tools expose it through provider-specific interfaces, so do not assume a JSON field will work in a query string, or vice versa. Check the documentation for the exact endpoint, spelling, authentication method, and accepted request format.
- Screenshot API:
user_agentin a POST JSON body. - ScreenshotCenter:
user_agentas an optional query parameter; its help article also shows a JSON request object. - shot-scraper:
--user-agenton the command line.
These are documented examples, not a shared standard. Documentation describing an input field does not by itself guarantee how every provider handles redirects or requests for page resources.
Send a User-Agent in Screenshot APIs
Screenshot APIs documents POST /v1/screenshot with a user_agent string in the JSON body. The request must provide either a target url or html. Its example uses an API key in the X-Api-Key header; bearer-token authentication is also documented. See the Screenshot APIs API reference for the provider’s current endpoint details.
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curl -X POST https://screenshotapis.org/v1/screenshot
-H "X-Api-Key: YOUR_API_KEY"
-H "Content-Type: application/json"
-d '{"url":"https://example.com","user_agent":"Mozilla/5.0 (compatible; ExampleBot/1.0)"}'
--output screenshot.pngReplace YOUR_API_KEY with your own key and use a User-Agent appropriate to your test. Keep credentials private; do not publish real keys in scripts or examples. The provider’s documented property name is user_agent, with an underscore.
Send a User-Agent in ScreenshotCenter
ScreenshotCenter’s endpoint reference documents user_agent as an optional query parameter. Use your HTTP client’s URL-encoding support because User-Agent values contain characters that should be encoded when placed in a URL. Confirm the endpoint and authentication details in the ScreenshotCenter screenshot endpoint reference; its custom headers help article also illustrates the field in a JSON request object.
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Do not copy the Screenshot APIs POST example unchanged for ScreenshotCenter: the request method and parameter placement must match the endpoint you are calling.
Set it with shot-scraper
For the command-line tool shot-scraper, use its documented --user-agent option:
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shot-scraper https://example.com --user-agent "Mozilla/5.0 (compatible; ExampleBot/1.0)"The option is a CLI flag, not a screenshot API request field. See the shot-scraper documentation for its command options and usage.
Check the capture and diagnose failures
A successful API response does not necessarily mean the intended page was captured. Verify the resulting image or PDF, and use any response status or diagnostic headers the provider supplies.
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- The request rejects the parameter: Confirm the exact spelling, endpoint, and transport. The examples here use
user_agentfor two hosted services and--user-agentfor shot-scraper; they are not interchangeable. - The capture shows a login or error page: Check the final page status and whether the target requires authentication or cookies. Screenshot API documentation says a final status of 401 or 403 indicates the screenshot is a login or error page rather than the intended content; see its status guidance.
- The initial page looks right but embedded content does not: Do not assume the configured User-Agent is applied identically to redirects and every subresource request. Consult the provider’s documentation or inspect the captured result.
- The page still blocks the capture: A User-Agent alone may not satisfy a site’s access requirements. Check supported headers, cookies, authentication, and capture options, and comply with the site’s terms and access rules.
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ScreenshotNeo accepts a User-Agent directly in a single GET request. Its parameter names also work with those used by other screenshot APIs, which can make switching easier. For example, this request saves a WebP capture:
curl -G "https://api.screenshotneo.com/v1/shot" -d access_key=YOUR_API_KEY --data-urlencode url=https://stripe.com -o shot.webpSee the ScreenshotNeo API documentation for request options. Before capture, it accepts cookie or consent banners and removes more than 60 known consent platforms, newsletter popups, and chat widgets; each cleanup step can be turned off. Bot checks or CAPTCHAs, blank pages, timeouts, failed loads, and cache hits cost nothing, and responses identify the page verdict and billing status in headers. An MCP server provides take_screenshot, get_page_info, and capture_pdf tools for Claude, Cursor, and other MCP clients. The free plan includes 1,000 screenshots a month with no card; paid plans start at $5 for 3,000 shots.
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Use a custom User-Agent responsibly
Set the value for a legitimate compatibility test or other permitted use. A changed User-Agent does not grant authorization, bypass access controls, or change the target site’s terms. If a site requires a login or explicit API access, use the supported route rather than relying on client identification.
Frequently Asked Questions
Is `user_agent` the same as the HTTP `User-Agent` header?
It is a provider’s request field for configuring the User-Agent sent during capture; the field itself is not a universal HTTP header name.
Can I use a custom User-Agent to bypass a CAPTCHA?
No. A User-Agent identifies a client; it does not authorize access or reliably bypass bot checks.
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