A “cannot connect to host” message from wkhtmltoimage does not, by itself, prove that the website is down. The failed load may be the main page, a referenced image or stylesheet, an invalid relative path, a local-file access restriction, or a remote resource the process cannot reach. Start by identifying the exact URL or path named in the complete error output; then troubleshoot that resource, not just the message.
First identify what failed
Before changing flags or network settings, capture enough information to reproduce the failure:
- The complete
wkhtmltoimagecommand and all stderr output. - The output of
wkhtmltoimage --version. - Your operating system or container, and whether a wrapper or library invokes the binary.
- Whether the input is a remote URL or a local HTML file.
- The exact resource URL or path mentioned in the error, with credentials and tokens removed from any shared logs.
Determine whether the failed load is the top-level document or a dependency such as an image, CSS file, font, or script. A page can load while one of its resources fails. In upstream issue #4408, a report involving wkhtmltoimage 0.12.5 described a missing relative image followed by an about:blank / ProtocolUnknownError message and exit code 1; that is one environment-specific report, not a universal definition of the error (upstream issue #4408).
Validate the failing URL or path
Check the actual resource named in stderr rather than assuming the page’s main address is the problem. Confirm the URL scheme, hostname, port, path, and any redirect destination. If it is a relative URL, verify that the page’s base URL makes that relative reference resolve to the intended location.
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For local files
Confirm that the file exists and that its path is expressed correctly for the operating system and invocation method. A malformed Windows file URL or path can fail independently of the local-file access policy. The explicitly named input HTML file and other local files referenced by it are not the same case: local-file restrictions concern access to additional local resources. See the historical Windows path discussion in upstream issue #1639, which was marked fixed in 0.12.2.
For remote resources
Check the full URL, including redirects. A page may redirect to a host that the runtime cannot reach, or an image or stylesheet may be served from a different host than the main document. Test access from the same host, container, service account, and proxy context that runs wkhtmltoimage; success from a developer’s laptop does not establish reachability from a server.
Allow access to local dependent files
If the failing reference is a local file, check whether local-file access is enabled for the invocation. The command-line documentation describes --allow <path> to permit access to a specified directory and --enable-local-file-access to allow local access more broadly; --disable-local-file-access is the restriction control. Prefer granting access only to the required directory when that is practical. Consult the wkhtmltoimage man page and the project usage documentation for the syntax supported by your build.
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For example, where the installed binary supports these options, a narrowly scoped command can look like:
wkhtmltoimage --allow /path/to/assets input.html output.png
Use the actual directory and input/output paths for your environment. If the input is a remote URL, adding local-file permissions will not repair a remote network failure.
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Check version and wrapper behavior
Defaults and option mapping can depend on the binary version and on how a wrapper constructs the page settings. Reports around version 0.12.6 describe changes or differences in local-file access behavior, while a Windows 10 report using 0.12.6 found that the enable flag alone did not resolve the reported access problem. Treat these as issue-specific observations, not guarantees. Verify the version of the binary actually launched and confirm that your wrapper passes the setting to the relevant page or object (go-wkhtmltopdf issue #55; upstream issue #5210).
Check reachability for remote resources
If the failing resource is remote, test the same hostname and URL from the same runtime context as the converter. Check hostname resolution, outbound firewall rules, proxy configuration, TLS or certificate requirements, and redirects to another host. The man page documents --proxy, --proxy-hostname-lookup, and repeatable --bypass-proxy-for controls; use the documentation for your installed build to confirm their syntax and effect (wkhtmltoimage man page). A proxy change is appropriate only when the resource is remote and the runtime’s network path requires it; it cannot fix a missing local file or incorrect URL.
Choose load-error handling without mistaking it for a fix
The command-line documentation lists abort, ignore, and skip handling for page and media load failures. These settings decide how the converter responds to a failed load; they do not make an invalid URL valid, restore a missing file, grant local permissions, or provide network access.
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| Policy | General effect | When to consider it |
|---|---|---|
abort |
Stop on a load failure. | When a complete, reliable capture requires all relevant content. |
skip |
Skip a failed resource or load. | When omission is acceptable and the output can be checked for missing content. |
ignore |
Attempt to continue despite a load failure. | When proceeding is preferable to stopping, with output validation afterward. |
Exact behavior depends on whether the setting applies to page loading or media loading and on the installed build. In issue #4408, an ignore setting did not prevent exit code 1 in the reported case, so do not assume that a policy setting will suppress every failure (upstream issue #4408). The command-line and library settings are documented in the man page and library settings reference.
Retest one change at a time
- Keep the original command, version, and full error output as a baseline.
- Change one likely cause only: correct the URL or path, adjust the local-access scope, fix wrapper option placement, or configure the required proxy or network route.
- Run the same input again and compare stderr, exit status, and output contents.
- If the failure remains, use the newly reported resource URL to determine whether the change exposed a second failing dependency.
This makes it easier to tell whether the cause was the main document, a dependent resource, or a policy/network setting.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Common failure patterns and fixes
- A relative image fails while the page URL looks correct: inspect the resolved image URL and the page’s base URL; correct the reference or ensure the referenced file is present.
- A local image or stylesheet is denied: validate the file path, then use a narrowly scoped
--allowpath or the supported local-access option. Confirm that the flag reaches the page through any wrapper. - The input is a Windows local path: verify that the path or
file:URL is correctly formed for the invocation, and distinguish the input document from additional local resources it references. - A remote asset fails only on the server: test from the converter’s runtime context and check DNS, outbound access, proxy settings, TLS requirements, and redirects.
- An error policy is set but the process still exits nonzero: treat the policy as failure handling rather than repair; inspect the exact failed resource and validate output and exit status.
Or skip the browser setup
If you need screenshots rather than specifically troubleshooting this legacy renderer, ScreenshotNeo is a website screenshot API and MCP server for developers. One GET request can return an image or PDF; the API supports PNG, JPEG, or WebP output. See the ScreenshotNeo documentation for request options.
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cURL example:
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Frequently Asked Questions
Does “cannot connect to host” always mean the website is down?
No. The failing load may be a dependent resource, a local file, or a remote host inaccessible from the converter’s runtime. Identify the exact resource in stderr first.
Can I use ScreenshotNeo to repair a wkhtmltoimage error?
No. ScreenshotNeo is an alternative screenshot API and MCP server; it does not repair wkhtmltoimage, its local paths, or its network configuration.
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