html2pdf.js is the most starred frontend HTML-to-PDF library, and countless tutorials recommend it. But it carries a structural flaw that no amount of configuration fixes: it converts your page through html2canvas into a bitmap image, then embeds that image into a PDF. The output is a picture of your document — text cannot be selected or searched, it blurs at high zoom, and files balloon in size. dompdf.js renders the same HTML through a Rust+WASM core and writes true vector PDFs, so text stays selectable and sharp and files stay small. This article compares the two libraries honestly across rendering principles, output quality, Chinese support, performance, and file size, shows both code paths side by side with a full feature comparison table, and walks through what a migration from html2pdf.js to dompdf.js actually involves, including a realistic step-by-step plan and the caveats you should know before switching. The comparison is written for teams that are already shipping with html2pdf.js and wondering whether the switch is worth the disruption. The migration section is deliberately concrete, with acceptance criteria you can reuse, because the hardest part of any migration is knowing when the new path is actually better than the old one.
html2pdf.js is a wrapper around two libraries: html2canvas renders the DOM into a Canvas bitmap, and jsPDF embeds that bitmap into a PDF file. The pipeline is HTML to image, then image to PDF — two lossy hops that define the library's ceiling, because the final quality can never exceed what the screenshot step captures.
The bitmap route has structural limitations. Text becomes pixels: it cannot be selected, searched, or copied. Zoom past 200% and edges visibly soften. Print the file and the difference from vector text is obvious on paper. For contracts, reports, and academic documents, these are deal-breakers that no configuration option can fix.
On top of that, html2canvas has incomplete CSS support. Complex backgrounds, certain flex and grid arrangements, some filters, and pseudo-element tricks render differently or not at all. Pages that look perfect in the browser can come out subtly wrong in the PDF, and the debugging sessions are notoriously long, often requiring attribute-by-attribute experimentation.
There are also well-known compatibility gaps: canvas, iframes, and cross-origin images each need their own workarounds, and the community has accumulated a large body of patch code over the years. Every one of those patches is maintenance debt, and the library's slower release cadence means browser fixes often lag behind.
The lossy pipeline also explains why html2pdf.js output is sensitive to timing. If a web font or an image has not finished loading when the screenshot is taken, the missing asset is baked into the PDF permanently — there is no re-render, only a retake. Teams end up adding sleep-based workarounds and image preloaders, which are fragile by nature and break whenever network conditions change.
Another structural limitation is page breaking. html2pdf.js slices the tall screenshot into page-sized chunks, which can cut a table row, a code block, or a paragraph across two pages at an arbitrary height. dompdf.js paginates by content: rows and blocks break at controlled points using CSS rules, which is the difference between a document that reads naturally and one that visibly interrupts mid-line.
The maintenance story is also part of the cost. html2canvas and jsPDF are separate projects with separate release schedules, so a fix in one can surface a regression in the other; debugging across that boundary is slow. dompdf.js is a single dependency with one release cadence, which shortens the path from 'something broke' to 'here is the fix' considerably.
Finally, consider the effect on your CSS. Because html2canvas does not support every property, teams often write export-specific CSS that only exists to make the screenshot come out right. The vector pipeline renders standard paged-media CSS, so those workarounds can be deleted rather than maintained, and the export stylesheet ends up smaller and closer to the design system.
dompdf.js implements its rendering core in Rust and compiles it to WebAssembly. The engine parses the HTML and CSS directly and emits PDF drawing instructions — there is no screenshot anywhere in the pipeline, and the output is a genuine vector PDF, which is architecturally cleaner than any screenshot-based approach.
Vector output means text is written as glyph outlines: selectable, searchable, copyable, and crisp at every zoom level. For documents that must be archived, indexed, or read on high-DPI displays, that is not a nice-to-have; it is the difference between a document and a picture of a document, and it cannot be measured in performance numbers alone.
dompdf.js also bundles Source Han Sans SC for zero-configuration Chinese, supports @page paged-media rules, automatic pagination, flex/grid layouts, and table borders — covering precisely the pain points that html2pdf.js users hit most often. The experience improvement after switching is immediate and visible.
Vector output has an accessibility bonus too: the text inside the PDF can be read aloud by screen readers, which satisfies accessibility requirements. A bitmap PDF is effectively a blank image to assistive technology — a hard compliance barrier in industries with strict document accessibility rules.
The vector pipeline also makes the output future-proof in a subtle way. A bitmap PDF is frozen at the resolution and quality of the moment it was captured; a vector PDF re-renders perfectly at any size, from a phone thumbnail to a large-format print. For documents with long shelf lives — contracts, certificates, archives — that re-renderability is worth a great deal.
Internally, the Rust core also handles resource reuse, so repeating elements such as logos and headers are stored once and referenced, rather than duplicated per page like screenshot pipelines do. That is one more reason the file size stays small on long documents, and it is a benefit you receive automatically without configuring anything.
Security is a quieter advantage: because the output is generated from parsed content rather than a screenshot of the user's screen, nothing extraneous — open tabs, browser chrome, unrelated UI — can leak into the file. Documents that will be shared externally benefit from that containment, since the PDF contains exactly what the template says and nothing else.
There is also an ergonomic win for developers: debugging a vector pipeline means inspecting HTML and CSS, the same tools used for the web page itself. Debugging a bitmap pipeline means squinting at screenshots and guessing which CSS property caused a glitch. The former is a normal development loop; the latter is a scavenger hunt, and the difference shows up in every bug report.
// ---- html2pdf.js: HTML -> Canvas bitmap -> PDF ----
import html2pdf from 'html2pdf.js';
const el = document.getElementById('report');
html2pdf()
.set({ margin: 10, filename: 'report.pdf' })
.from(el)
.save();
// Output is a bitmap: text unselectable, blurry when zoomed
// ---- dompdf.js: HTML -> vector PDF ----
import { DomPDF } from 'dompdf.js';
const pdf = new DomPDF();
pdf.addPage(document.getElementById('report'), {
format: 'A4',
margin: '10mm',
});
pdf.save('report.pdf');
// Output is vector: text searchable, sharp at any zoom| Dimension | html2pdf.js | dompdf.js |
|:---|:---|:---|
| Output type | Bitmap (screenshot embedded) | Vector PDF |
| Selectable / searchable text | No | Yes |
| Sharpness at 200% zoom | Blurry | Crisp |
| Chinese support | Depends on page fonts | Bundled Source Han Sans SC |
| Pagination | Height-based cutting, may clip | CSS-driven, precise |
| Large-document performance | Slow, page-by-page screenshots | Fast, ~1000 pages in 2s |
| File size | Large (whole-page images) | Small (vector) |
| Dependencies | jsPDF + html2canvas | Single library |
| Bundle size | Large | Small |html2pdf.js renders each page by re-running html2canvas and encoding the result as an image. Every additional page adds a full screenshot cycle, so long documents get slower and memory-hungrier; beyond ten pages the experience degrades noticeably, and very long pages can fail outright, which makes the library risky for serious batch workloads.
dompdf.js's WASM pipeline skips image encoding entirely. Rendering throughput stays flat: roughly a thousand pages in about two seconds, with file size growing linearly with content rather than exploding with page dimensions. Performance is predictable, which matters for production exports and heavy batch jobs.
On mobile and low-end devices the gap widens further. Bitmap pipelines pay extra memory and decode costs per page; the vector pipeline has a shorter render path and lower peak memory, which makes browser-side PDF generation on phones noticeably more stable and cheaper to support.
From a development perspective, html2pdf.js's many configuration options mostly exist to patch known defects, while dompdf.js needs almost no configuration at all. Teams pick it up faster, new hires produce working features sooner, and the reduced configuration surface lowers training and hiring costs over the life of the project.
Predictable performance also matters for testing. With a bitmap pipeline, a 50-page export is a heavy integration test that flaky networks can break; with the vector pipeline, generation is fast enough that tests can export full documents on every commit. Teams that add a PDF smoke test to CI find that the vector approach makes the test suite both faster and more reliable.
User perception follows the same curve. A two-second export feels instant, and users retry exports out of impatience — each retry wasting more resources. Removing the wait removes the retry loop, which reduces load on any downstream storage and improves the product's reputation for reliability at the same time.
For teams supporting multiple locales, the bundled CJK font removes a whole class of regional testing. html2pdf.js output depends on which fonts the viewing machine happens to have installed; dompdf.js renders the same glyphs everywhere, so a document tested in one office behaves identically in another — a consistency win for distributed teams.
Migrating from html2pdf.js is inexpensive because the interfaces are similar: both accept an HTML element or markup and produce a downloadable PDF. The core change is swapping html2pdf().set({...}).from(el).save() for new DomPDF() plus addPage plus save, which a competent developer can do in half a day.
During migration, check three things: whether CSS that html2canvas handled specially renders identically in dompdf.js, how custom headers and footers are implemented in your current setup, and how images load in your pages — inlining them as base64 removes a whole class of timing problems before they can occur.
One honest caveat: html2pdf.js's community is much larger, so answers to niche questions are easier to find, while dompdf.js's community is younger and some edge cases require reading the source. But the underlying direction — vector over bitmap — is the technically correct one, and the sooner a project moves, the less rework it inherits.
A phased rollout reduces risk: adopt dompdf.js for new feature modules first while existing modules stay on html2pdf.js, then migrate legacy pages one by one once stability is proven. Define acceptance baselines for sharpness, file size, generation time, and pagination, and compare before and after with real numbers rather than impressions.
One more perspective: if you only export simple pages occasionally, html2pdf.js's convenience is still worth keeping — there is no need to switch for the sake of switching. When document complexity, page counts, or quality requirements rise, that is the moment to evaluate the vector path; upgrading on demand is the most prudent approach.
Communication matters as much as code in a migration. Tell users what changes and what does not: the exported file may look subtly different because rendering engines differ, and that is expected — the acceptance criteria you define beforehand are what make the difference a feature rather than a complaint. A short changelog entry plus a sample of before-and-after exports answers most questions before they are asked.
Watch the long tail of edge cases: pages that rely on web fonts with exotic subsets, elements using CSS filters, and very wide tables. Each has a known equivalent in the vector world, but the first migration is the time to catalog them. Keep a regression list during the transition and re-test it after every dompdf.js upgrade, so the migration's lessons become a permanent safety net rather than a one-time effort.
One caveat about expectations: do not expect pixel-identical output, because the two engines measure and lay out differently. Expect equivalent quality at the document level — sharp text, correct pagination, complete content — and verify those properties with the acceptance baselines rather than side-by-side pixel comparisons, which will always show minor differences.
Roll back is easy too: because both libraries produce a downloadable PDF from the same HTML, keeping the old export path behind a feature flag costs almost nothing. If a blocking issue appears in production, flipping the flag restores the previous behavior while the fix is developed — a low-risk way to run the migration.
下面的按钮用 dompdf.js 在浏览器端实时生成 PDF，无需后端：
这是由 dompdf.js 渲染的示例 PDF 内容。