Short answer: wkhtmltopdf renders an HTML page through Qt WebKit and is the closer fit when you already have HTML to convert. FPDF is a PHP library for building PDF pages with drawing, text, image, and layout calls; its optional HTML parser handles only a small subset of markup, not arbitrary web pages. There is no defensible head-to-head speed result in the available sources, so choose by input model and test representative documents on your intended host.
How wkhtmltopdf and FPDF differ
| Question | wkhtmltopdf | FPDF |
|---|---|---|
| What does it take as input? | A URL or HTML document that it renders through Qt WebKit. | PHP code that constructs PDF content through its document-layout API. |
| Does it render a website? | It is an HTML-to-PDF command-line converter. Its output depends on the HTML, assets, build, and rendering behavior. | Not as a browser would. Its tutorial shows a limited parser for selected HTML tags; the FPDF FAQ says it does not convert real-world pages. |
| Where does layout come from? | From the HTML/CSS page being rendered, subject to the renderer’s capabilities. | From explicit calls to place text, images, links, and page elements. |
| What is the main trade-off? | Reuse existing HTML, but accept an older rendering stack and carefully assess security and deployment. | Build predictable document layouts in PHP, but implement the layout rather than handing it a complete web page. |
They are not interchangeable implementations of the same renderer. A comparison based only on which one is “faster” misses the first decision: whether the source document is a web page or a PDF layout authored in code.
Can FPDF convert HTML to PDF?
Not in the general browser-rendering sense. FPDF’s tutorial demonstrates a small WriteHTML parser based on regular expressions. The example supports a limited set of tags and behaviors, including bold, italic, underline, anchor links, and line breaks. The FPDF FAQ’s answer to whether it can convert an HTML page to PDF is “Not real-world pages.”
Contributed scripts may support additional tags, but their capabilities depend on the specific extension. A parser for selected markup is not a CSS layout engine: do not assume that a page’s stylesheet, responsive layout, JavaScript, remote assets, or browser-specific behavior will be reproduced. If you choose FPDF, treat the PDF as a document to compose with its API, and use an HTML helper only when your markup fits the helper’s documented subset.
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When to choose each tool
Choose wkhtmltopdf when
- You have controlled HTML that should be rendered as a page rather than rebuilt as PDF drawing commands.
- Your templates have been checked against wkhtmltopdf’s particular rendering behavior, and any CSS, fonts, images, or page-break needs are verified in the exact build you will deploy.
- You can operate the binary and its dependencies on your target OS and architecture, and can isolate the conversion process appropriately.
Choose FPDF when
- Your application already runs PHP and the document can be laid out directly as text, images, links, and pages.
- You want explicit control over page formats, margins, headers and footers, automatic page breaks, fonts, and compression through a PDF-oriented API.
- You do not need a browser to interpret arbitrary HTML and can manage PHP memory and execution-time limits for the documents you generate.
Consider a different renderer when
If your HTML depends on modern or dynamic JavaScript, the wkhtmltopdf project status page suggests Puppeteer for dynamic-JavaScript pages and names WeasyPrint or Prince for report generation. These are candidates to evaluate, not automatic drop-in replacements: verify their current maintenance, requirements, licensing or terms, and output against your own templates. ScreenshotNeo is another alternative to try first when the actual job is capturing a live webpage as an image or PDF rather than converting a document template. Its API is at ScreenshotNeo; it is not a replacement for a general-purpose HTML-to-PDF renderer.
How to use wkhtmltopdf and FPDF
Render a local HTML file with wkhtmltopdf
After installing a build suitable for your OS and architecture, a basic conversion from a local file is:
wkhtmltopdf input.html output.pdfThe project also documents URL input, page objects, cover pages, table-of-contents objects, and command-line options. Check the options supported by your installed binary, especially when relying on features that require patched Qt; distribution builds without those patches can behave differently. Make remote assets and fonts available to the conversion process, and validate page size, margins, pagination, and links in the resulting PDF.
Build a PDF with FPDF
FPDF’s API workflow is to create a document, add pages, set fonts, and issue calls that place content. The exact calls depend on the PHP package version and the layout you need; consult the official tutorial and API documentation for the chosen version. The tutorial’s WriteHTML example is an optional restricted parser, not a way to feed any website into FPDF. If you use a contributed HTML script, verify its supported tags and behavior before relying on it.
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Performance: is wkhtmltopdf faster than FPDF?
The available evidence does not establish a fair speed winner. FPDF’s homepage makes a qualitative speed comparison with PDFlib, not wkhtmltopdf. A public multi-engine benchmark includes wkhtmltopdf in its fixture set but excludes it from latency comparisons because the Docker emulation would not provide a fair speed comparison; that benchmark does not include FPDF. Neither source answers the pairwise question.
The tools also do different work. Rendering a complex page with external assets and composing a text-and-table report through a PHP API are not equivalent workloads. A useful comparison needs the same document requirements and a clear account of what the measurement includes. Benchmark on the machine or container you plan to run in, using representative documents and the exact builds you intend to deploy.
Make a useful local benchmark
- Record each renderer and library version, OS or container image, CPU and memory limits, and relevant PHP extensions or Qt build.
- Use representative HTML or PDF layouts, including typical and largest documents, fonts, images, remote assets, and page counts.
- Measure end-to-end latency and peak memory at the concurrency you expect. Report cold and warm runs separately and say whether process startup is included.
- Run multiple iterations and report the method, such as median and a clearly identified percentile, rather than a single best time.
- Compare output correctness as well as time: page count, clipping, font substitution, missing assets, and pagination can make a fast result unusable.
Do not transfer a result from a different renderer, emulated environment, or document shape to your workload.
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wkhtmltopdf needs a deliberate trust boundary
The wkhtmltopdf project status page describes its Qt 4/WebKit base as old and warns against feeding it untrusted HTML or JavaScript without sanitization. The warning is the project’s security guidance; it does not establish that a specific vulnerability affects every deployment. Treat user-controlled markup and scripts as hostile input: sanitize according to your application, restrict what the conversion process can access, and consider process-level controls such as AppArmor or SELinux. Avoid running conversions with broad access to application secrets or the host filesystem.
The official downloads page lists wkhtmltopdf 0.12.6 as stable and gives June 11, 2020 as its release date. That page may not describe every later packaging or security development, so verify the exact binary, build variant, platform, and maintenance status before adopting it. A version number alone does not establish that two builds have the same patched-Qt features or behavior.
FPDF has application-level resource limits
FPDF runs as PHP code rather than as a web renderer, but generating large PDFs can still hit PHP memory limits, particularly when images are involved. Execution-time limits can matter as well. Measure with realistic document sizes, handle failures in the calling application, and set resource limits appropriate to your service instead of assuming that a small sample predicts production behavior.
Plan for reproducible output
For either path, pin the relevant runtime and dependencies where practical, keep test documents that exercise fonts and page breaks, and compare generated PDFs after upgrades. For wkhtmltopdf, include the exact binary build and its asset-loading environment in the record. For FPDF, include the PHP runtime, library version, extensions, and font files. These details help explain why a PDF changed across machines or deployments.
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If your goal is a clean capture of a live page rather than a custom report generated from HTML, ScreenshotNeo can return a screenshot or PDF from one GET request. Its API accepts a URL and returns PNG, JPEG, WebP, or PDF; see the ScreenshotNeo API documentation.
curl -G "https://api.screenshotneo.com/v1/shot" -d access_key=YOUR_API_KEY --data-urlencode url=https://stripe.com -o shot.webpBefore capture, it accepts the cookie or consent banner as a visitor and removes 60+ known consent platforms, newsletter popups, and chat widgets; each of those steps can be turned off. Bot checks, blank pages, timeouts, failed loads, and cache hits cost nothing, and responses identify the page verdict and billing status in headers. Its MCP server provides take_screenshot, get_page_info, and capture_pdf tools for AI agents, including Claude, Cursor, and other MCP clients. The free plan includes 1,000 screenshots per month with no card; paid plans start at $5 for 3,000. This is useful for web-page capture, not a substitute for constructing arbitrary report layouts in FPDF or rendering every HTML document as a PDF.
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HTML looks different in the PDF
With wkhtmltopdf, first confirm which binary and build you are running, then test the specific CSS, fonts, page breaks, and asset URLs in a minimal fixture. Do not assume a feature behaves identically across patched and unpatched builds. With FPDF, check whether the layout is actually being composed through its API or whether an HTML helper supports the tags you supplied; unsupported page styling will not become browser rendering automatically.
Images or fonts are missing
For wkhtmltopdf, make sure the conversion process can reach the asset URLs and that the deployed build can load the required resources. For FPDF, confirm the font is registered or embedded as required by your implementation, and that image formats are supported by the library and extensions installed. Check logs and test from the same host or container as production.
Large FPDF output exhausts memory or times out
Reduce unnecessary image size, inspect PHP memory and execution-time limits, and measure the largest expected document. The FPDF FAQ specifically notes that large documents, particularly those containing images, can encounter these PHP limits.
wkhtmltopdf behaves differently across deployments
Record the build source and Qt patch status, OS and architecture, and fonts and assets available to the process. The project’s downloads page notes that some features require patched Qt and that distribution builds without those patches can behave differently. Validate output using the actual deployed binary.
Which should you use for HTML-to-PDF generation?
Use wkhtmltopdf only when rendering your existing, controlled HTML through its older Qt WebKit behavior is acceptable and you can validate the binary, security boundary, and deployment. Use FPDF when you can author the document as PHP-driven PDF layout and want direct control over page elements. If neither input model fits—especially for dynamic JavaScript or print-focused requirements—evaluate a currently maintained renderer against your templates. Decide with output fidelity, security, compatibility, and a workload-specific benchmark, not an unsupported blanket claim about speed.
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Frequently Asked Questions
Does FPDF support HTML at all?
Yes, limited helpers and contributed scripts can parse selected tags. That is distinct from converting arbitrary real-world pages through a browser engine.
Does wkhtmltopdf execute JavaScript?
It renders through Qt WebKit, but the supplied sources do not establish support for every modern or dynamic JavaScript use case. Test your page; the project suggests Puppeteer for dynamic-JavaScript pages.
Is FPDF still compatible with PHP?
The FPDF changelog lists version 1.9, dated May 31, 2026, with PHP 5.3 as the minimum. Check the changelog and your required extensions for the exact deployment.
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