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Repair common Windows errors and clear accumulated junk for a smoother, more stable PC - no reinstall needed.Free scan · no reinstallUse wkhtmltopdf --run-script 'your JavaScript here' input.html output.pdf. The option supplies JavaScript that wkhtmltopdf runs after the page has finished loading; it can be repeated to run more than one script. For example: wkhtmltopdf --run-script 'document.body.classList.add("ready")' https://example.com output.pdf. The command-line manual documents this behavior for wkhtmltopdf 0.12.6 with patched Qt. Read the manual.
What –run-script does, and where it goes
wkhtmltopdf converts an input object, such as a webpage or HTML file, into an output document. The --run-script <js> option provides additional JavaScript for the page. Put the option and its JavaScript argument before the input and output paths:
wkhtmltopdf [options] input.html output.pdf
For example, this command adds a class to the document body before rendering:
wkhtmltopdf --run-script 'document.body.classList.add("ready")' https://example.com output.pdf
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The shell quotes group the JavaScript into one argument; they are not part of the script. Adjust quoting if your script or shell requires it. This is a syntax example, not a claim that the conversion has been tested against that page.
The manual says JavaScript is enabled by default and that each --run-script is run after the page is done loading. The option is repeatable, so you can supply it more than once:
wkhtmltopdf --run-script 'document.body.classList.add("ready")' --run-script 'document.title = "Captured report"' input.html output.pdf
These scripts are passed as JavaScript text. The manual does not describe a form that takes a path to a JavaScript file, so do not assume that --run-script script.js loads a file. If you need to maintain a larger script, put its logic in the page or use a wrapper that reads the file and passes its contents as the option argument, taking care to quote and validate the resulting command safely.
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“Page done loading” is not the same as “all asynchronous work is finished.” A page can still fetch data, render content, or load images after its initial load event. The manual does not promise that --run-script waits for arbitrary asynchronous JavaScript started by the page or by the supplied script.
Wait for a readiness signal
For a page you control, arrange for the page to set window.status to a known value only after the content needed in the PDF is ready. Then ask wkhtmltopdf to wait for that value:
wkhtmltopdf --window-status report-ready input.html output.pdf
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The page must actually set window.status to report-ready; otherwise wkhtmltopdf may keep waiting. This is useful when readiness depends on a known application event, rather than a guessed number of seconds. The manual documents --window-status <windowStatus> as a wait control. See the option reference.
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Use a fixed JavaScript delay when appropriate
If the page behavior is predictable but has no readiness signal, use --javascript-delay <msec> to allow time after loading. The 0.12.6 manual lists a default delay of 200 milliseconds. Set a value based on the work your page actually performs, then inspect the generated PDF; there is no universally correct delay for all sites.
A delay is a time allowance, not proof that a particular request or rendering operation completed. Making it longer can also make every conversion slower. Prefer a readiness signal when you can reliably define one.
Understand slow-script behavior
The manual says wkhtmltopdf stops slow scripts by default and documents --no-stop-slow-scripts to change that behavior. This setting is separate from deciding when the page is ready: disabling the stop behavior does not itself establish that the output contains all desired content. A script that loops indefinitely can also prevent useful progress, so use this option only when you understand why a legitimate script runs slowly.
Quoting JavaScript safely in a command
Shell quoting determines what reaches wkhtmltopdf. The single-quoted example works in common POSIX shells when the JavaScript contains no single quote. If the script contains a single quote, either change the JavaScript string delimiters or use shell-appropriate escaping. For example, this uses double quotes inside the JavaScript and single quotes around the whole argument:
--run-script 'document.querySelector("#status").textContent = "Ready"'
When building commands programmatically, avoid concatenating untrusted page content or user-supplied JavaScript into a shell command. Prefer a process API that passes arguments separately, and apply the security precautions below.
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Check your wkhtmltopdf build before relying on an option
The online generated manual identifies itself as wkhtmltopdf 0.12.6 with patched Qt. The project’s downloads page calls 0.12.6 the stable series and gives its release date as June 11, 2020. Builds distributed by operating systems may differ, and the project notes that platform builds can behave differently.
- Run
wkhtmltopdf --versionto identify the executable available on your system. - Run
wkhtmltopdf -Hand check whether your build lists--run-script,--javascript-delay, and--window-status. - Try a small conversion with a page you control and inspect the resulting PDF before deploying the command in a larger workflow.
The project says its generated manual corresponds to the help displayed by wkhtmltopdf -H. If the local help differs from the online manual, treat the local executable’s output as the relevant reference for that installation. Sources: project downloads and documentation index.
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Security: do not render untrusted HTML or JavaScript casually
The wkhtmltopdf downloads page warns that untrusted HTML can be dangerous and says user-supplied HTML or JavaScript must be sanitized; otherwise, it can lead to complete takeover of the server running the converter. A PDF conversion process should not be treated as a safe sandbox merely because its output is a document. Read the project’s warning.
- Render only content you control or have properly sanitized.
- Do not pass arbitrary user-provided script text to
--run-script. - Run conversions with only the operating-system permissions and access the job needs, and isolate the process from sensitive files and services where possible.
- Keep command arguments separate when invoking wkhtmltopdf from application code; do not interpolate untrusted values into a shell command.
Troubleshooting missing or incorrect output
The script appears not to run
Check that JavaScript is not disabled by another option, that your installed build recognizes --run-script, and that the option appears before the input object. Test with a simple visible change, such as changing the page title or adding a class, rather than starting with a complex application script. Confirm the result by inspecting the PDF, not just the command’s exit behavior.
The PDF misses content created by JavaScript
The page may finish its initial load before the relevant asynchronous work completes. Use --window-status with a readiness value your page sets after rendering the content, or set a considered --javascript-delay and verify the output. Do not assume that adding --run-script causes all page scripts or network activity to finish.
The command reports an option or argument error
Check the local wkhtmltopdf -H output, the order of the option and its argument, and shell quoting. The JavaScript must arrive as one argument. If using a wrapper or application, inspect how it splits and escapes arguments rather than adding more quote characters blindly.
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Look for scripts that wait forever for an event or continually schedule more work. Confirm that any window.status readiness value can actually be reached. The manual documents stopping slow scripts as the default and provides --no-stop-slow-scripts; changing that behavior is not a general remedy for an application that never reaches a stable state.
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Results differ from another machine
Compare --version and -H output on both systems. The online manual covers 0.12.6 with patched Qt, while the project cautions that platform builds can behave differently. Do not assume that a command verified for one packaged build behaves identically on another.
When wkhtmltopdf may not be the right renderer
The wkhtmltopdf project describes its Qt/WebKit foundation as outdated. For a site that depends on dynamic JavaScript, the project suggests considering Puppeteer. For generating reports from HTML you control, it also names WeasyPrint and commercial Prince as alternatives. These are the project’s recommendations, not results from a comparative test. See the project status page for its context.
If your requirement is to capture a page as an image or PDF through an API rather than manage a local HTML-to-PDF process, ScreenshotNeo is a separate option: it accepts a URL and returns PNG, JPEG, WebP, or PDF. It does not make wkhtmltopdf’s JavaScript execution more reliable; it is an alternative capture workflow.
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ScreenshotNeo lets you request a screenshot or PDF with one HTTP call. For example, save a PDF using cURL:
curl -G "https://api.screenshotneo.com/v1/shot" -d access_key=YOUR_API_KEY --data-urlencode url=https://example.com -o page.pdf
Replace YOUR_API_KEY with your key. See the ScreenshotNeo API documentation for request options and response details. The same endpoint supports PNG, JPEG, and WebP as well as PDF.
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