In the ever-evolving landscape of web development tools, capturing and converting DOM elements to images remains a common challenge for developers. The recently released snapDOM library promises to convert HTML elements into scalable SVG images with high fidelity, but community testing has yielded mixed results that challenge some of the tool's core claims.
Performance Claims Under Scrutiny
The snapDOM library claims to be extremely fast at capturing DOM structures, with benchmark tests suggesting it outperforms popular alternatives like html2canvas and modern-screenshot, especially for larger elements. According to the documentation, snapDOM becomes dramatically faster as DOM size increases, with claims of being up to 15.98x faster than html2canvas for very large elements.
However, real-world testing by developers has contradicted these performance claims. One developer who has been using html2canvas extensively for their basketball simulation website reported opposite results:
I've been using html2canvas for a long time so I gave your library a try. It was much slower (I know your README has benchmarks saying the opposite so idk) and the result looked a lot worse.
The developer shared comparison screenshots that appeared to show html2canvas producing better visual results than snapDOM, raising questions about the benchmark methodology used in the library's documentation.
snapDOM vs Alternatives Benchmark Claims
| Element Size | Winner | vs modern-screenshot | vs html2canvas |
|---|---|---|---|
| 200x100 (Small) | modern-screenshot | 1.18x faster | 4.46x faster |
| 400x300 (Modal) | snapDOM | 1.04x faster | 4.07x faster |
| 1200×800 (Page view) | snapDOM | 2.43x faster | 5.74x faster |
| 2000×1500 (Large scroll area) | snapDOM | 5.02x faster | 9.35x faster |
| 4000×2000 (Very large) | snapDOM | 11.35x faster | 15.98x faster |
Note: These are the claims made in the snapDOM documentation, but real-world testing by some developers has yielded contradictory results.
Technical Implementation and Limitations
snapDOM uses SVG's foreignObject element to embed HTML content, a technique that allows for potentially better scaling compared to canvas-based solutions. This approach has sparked technical discussions about the fundamental differences between SVG and canvas-based capture methods.
One community member questioned how SVG could possibly be faster and more accurate than canvas, especially when dealing with complex CSS features like shadows. Another developer explained that snapDOM embeds HTML directly in SVG via foreignObject, though they expressed uncertainty about whether this approach would be more reliable or consistent across different viewing environments.
The library creator acknowledged some early challenges with file size optimization, noting: I was upset about the size of generated svg file because at first all styles were inlined in each element. So I created a function to make mini css classes (.c1, c2, c3,...) So the final size is quite small.
Cross-Browser and Environment Compatibility
Several developers inquired about snapDOM's compatibility with different environments beyond standard web browsers. When asked about browser extension compatibility, the developer admitted they hadn't tested it in that context. Similarly, when questioned about Node.js compatibility with DOM polyfills, the creator indicated this hadn't been tested yet.
The library does appear to work across major browsers, with the developer confirming testing on Chrome, Firefox, and Safari. This stands in contrast to some alternative approaches mentioned in the discussion, such as the Media Capture API, which currently has limited browser support.
Key Features of snapDOM
- Converts HTML elements to scalable SVG images
- Preserves styles, fonts, backgrounds, shadow DOM content, and pseudo-elements
- Export options: SVG, PNG, JPG, WebP, or canvas
- No dependencies, uses standard Web APIs
- Special handling for shadow DOM and pseudo-elements
- Element exclusion and placeholder options via data attributes
Feature Requests and Future Development
The community discussion revealed interest in additional features, with one developer suggesting PDF export functionality. While the creator considered this outside the current scope, they acknowledged it might be possible using external libraries like jsPDF or svg2pdf.js.
Other developers requested improved documentation with visual examples showing the library's output. As one commenter noted, Image in the readme would really be helpful. In fact anytime there is a visual output it makes sense to put an image.
As snapDOM continues to evolve, these community insights may help shape its development roadmap and improve its utility for real-world applications. For now, developers appear to be weighing its unique SVG-based approach against more established tools like html2canvas, with practical considerations like performance, visual accuracy, and cross-environment compatibility being key factors in their evaluation.
Reference: snapDOM