John Smith's Blog

Ramblings (mostly) about technical stuff

What's the best way of including SVGs in a responsive web page?

Posted by John Smith on

TL; DR: <object> seems the best bet - although Safari 5.1 has issues compared to the other browsers. Second choice is having the SVG inline in the HTML, but that has issues for WebKit and IE.

As a diversion from my more usual diet of Python, I've spent a fair bit of time over the past week or so revisiting SVG. My previous experiments have usually been done using fixed sizes, but I've always wanted to do something that fits in better with what these days is called "responsive design", especially given as these are supposed to be scalable vector graphics.

For an example of the sort of thing I've been aiming for, take a look at the main chart on a Google Finance page. This Flash chart resizes horizontally as you change the size of the browser window. (NB: the chart makes extra data visible as you make the browser window wider, which isn't exactly what I want, but you should get the idea.)

Unless I've been particularly boneheaded about the way I've investigated this, this isn't as straightforward a problem as it first seemed. If you put a regular bitmap image in an HTML page with something like <img src="whatever.png" width="100%" /> the image will scale as you'd hope when the browser window is resized. This isn't necessarily the case with SVG.

As outlined in the W3C docs, there are five ways that you can pull SVGs into a page in a modern browser:

  • <embed>
  • <frame> / <iframe>
  • <object>
  • <img>
  • Inline <svg>
(You can also create an SVG via DOM function calls, but I'm not particularly interested in that approach right now.)

I've built tests for each of these, and run them through the latest versions of the five main browsers. This obviously ignores a lot of issues with older browsers and mobile browsers, many of which don't even support SVG at all, but as it turns out, the "big 5" are enough to worry about on their own :-(

In the following sections, when I refer to a particular browser, the tests were done in the following versions, which (AFAIK) are the current ones as of early April 2012:

  • Firefox 10
  • Opera 11.62
  • Chromium 17 or 19 (I didn't notice any difference between the two
  • Internet Explorer 9
  • Safari 5.1
Where relevant, issues are illustrated with screengrabs from the Windows version of a browser, but much of my testing was done with Linux versions - except in the case of IE and Safari. I also tested whether JavaScript functionality worked - both within the SVG itself, and from the enclosing document trying to manipulate the SVG.

Just for clarity's sake: all of this messing around is (probably?) only needed if you want an SVG to be scalable within your web page. If you're happy for it to be a fixed size, then you shouldn't have to worry about any of the following stuff.


Test link:

The image gets scaled correctly in Firefox, Chromium and IE. The image does not get scaled correctly in Opera or Safari.

Screengrab of SVGs using the embed tag in Opera 11.62 Screengrab of SVGs using the embed tag in Safari 5.1


Test link:

(I've assumed <frame>s behave the same; I couldn't be bothered to write a separate test for them.)

Only Chromium rendered the page completely as desired. Screengrab of SVGs using the iframe tag in Chromium 19

IE and Safari both failed to scale the images properly, but were able to modify the SVGs from the enclosing document's JavaScript. Screengrab of SVGs using the iframe tag in IE9 Screengrab of SVGs using the iframe tag in Safari 5.1

Firefox and Opera failed to scale the images, or modify them via the JavaScript in the enclosing document. I'm not sure if the JS issue is down to some DOM API difference and/or security problem - but as the scaling is broken, I couldn't be bothered to investigate further. Screengrab of SVGs using the iframe tag in Firefox 10 Screengrab of SVGs using the iframe tag in Opera 11.72

(All browsers did at least run the JavaScript contained within the SVG files.)


Test link:

Only Safari lets the side down, by failing to scale the SVGs. All other browsers work as desired. Screengrab of SVGs using the iframe tag in Safari 5.1


Test link:

If you have any JavaScript-based interactivity, forget about using <img> tags - the JS in the SVGs won't be run, and the JS in the document doesn't do anything either. WebKit-based browsers also have weird issues with additional padding and squashed images. You might hope that the preserveAspectRatio might be able to solve that, but I was unable to find any value which fixed things. Screengrab of SVGs using the img tag in Chromium 19 Screengrab of SVGs using the img tag in Safari 5.1

Inline <svg>

Test link:

This method is what the BBC uses for the position chart in its football tables, which is the highest profile use of SVG in a mainstream site that I know of.

Scaling works in all browsers, except IE. Screengrab of SVGs using inline SVG in IE9

However, WebKit browsers suffer from excessive vertical padding - it seems that WebKit assumes the height of the image is the same as the browser window, rather than the viewBox attribute in the <svg>. A slightly messy fix is to manually alter the height of the SVG elements after the page has loaded - this wasn't incorporated into this particular test, but an example from another test is here, and other people have documented similar workarounds. There are some open bugs on the WebKit tracker that might be related, here and here. Screengrab of SVGs using inline SVG in Chromium 19 Screengrab of SVGs using inline SVG in Safari 5.1

Whilst doing some earlier tests in this area, I also found a couple of bugs in Opera where

  • An HTML5 page wouldn't properly render, and would never trigger the load event - but an effectively identical XHTML page was fine. Warning: this bug also causes Opera to consume 100% CPU on the processor it is running on Screengrab showing bug in Opera in HTML5 page with embedded SVGs
  • If a page had multiple copies of the same SVG pulled in via the <img> tag, then if the page was reloaded, most of the duplicates would not appear: Screengrab showing bug in Opera after a page with duplicate SVGs is reloaded
Both of these have been reported to Opera via the tool built into their browser


As can be seen, of the five methods available, none is 100% foolproof. It seems to me that the best bet is <object>, as it works fine on all browsers except Safari, without need for JavaScript hacks. Second-place is embedding the SVG into the HTML, which entails a simple hack for WebKit browsers - but unfortunately is still broken in IE.

Disparity in requestAnimationFrame behaviour between Chrome and Firefox

Posted by John Smith on

This is a brief prelude to another post I hope to make in a couple of days or so, once I've solved my problem to my satisfaction. In the meantime, here's a related curio that I hadn't seen documented online before I had to start digging...

requestAnimationFrame is something that's been pushed in the last year or two as a more efficient way of doing animations in JavaScript than the traditional technique of using setInterval. In particular, it aims to avoid having your machine burn CPU on executing animations in a tabbed page that's not currently visible.

At time of writing, only Firefox and Chrome seem to actually support this function, albeit with moz and webkit vendor prefixes. doesn't have too much information about future support in other browsers - it'll appear in IE10, but it's unclear about Safari or Opera. Certainly the Opera Next 12.0 I downloaded yesterday doesn't appear to have it.

Now, for the most part this isn't the end of the world, as there are published shims to implement a workable alternative using setInterval() or setTimeout(). Unfortunately, these will just churn away as normal in a background tab, whereas what I wanted to do was to see how things were different in a background tab.

It turns out that the two implementations we have so far differ in their behaviour. Chrome comes to a dead stop when a page is in a background tab, which is probably what you'd naively expect to happen. Firefox on the other hand does some gradual throttling - you'll get one frame in the first second of being backgrounded, then another after a further two seconds, then a further four seconds, eight seconds, sixteen seconds, etc.

I knocked up a very rough demo for this, so that you can see for yourself - take a look here, and see what happens when you r-click the link on the page and open it in another tab - the function called via requestAnimationFrame() updates the page title, so you can see how often it gets called from the text in the tab.

I'm not completely clear why Mozilla have implemented this the way they have - I've not dug out any official specs, but going by the year old Chromium issue to add this functionality, I don't expect this behaviour to show up in Chrome/Chromium.

In the next post I'll elaborate on the problem I've been trying to solve - suffice to say, using requestAnimationFrame was a bit of a hacky way of trying to achieve something that I'd have thought should have been extremely straightforward...

Helvetica is dangerous

Posted by John Smith on

For the past couple of months or so, I've been using the "Minefield" nightly builds of Firefox 4.0 rather than the "official" 3.6.x releases - 4.0 truly is an upgrade that merits the increment of the major version number.

It therefore came as a bit of a shock when I viewed this blog using 3.6.12 on my Mac - just about all the text was showing in an italic (or possibly oblique) typeface! My initial panic subsided when I confirmed that everything still looked as expected in every other browser, but this didn't get any closer to resolving the issue. Using Firefox's "Inspect Element" functionality gave no further clues, insisting that the text was in a regular font, despite the evidence in front of my eyes.

A quick hack-up of an HTML test file proved that I wasn't going insane, and that there is in fact a bug in Firefox 3.6:

Screen grab from Firefox 3.6 on Mac OS X, showing Helvetica text rendered at different font-weights.  The text at lower weights is italicized

Some cursory Googling didn't find any reports of exactly the same issue, but this thread (started by no less than Jeffrey Zeldman!) covers similar ground.

I did try explicitly setting the font to be Helvetica Neue Light, but it transpires that Firefox ignores this, and requires you to use font-weight, which as we've just seen is broken - thanks a bundle...

As the bug seems to have been around for a while, and is fixed in the 4.0 betas, I don't hold out much hope of it being rectified in the 3.6.x releases. As a workaround, I've fallen back to using Arial for the headings, as does work correctly with the lower font-weight values.

About this blog

This blog (mostly) covers technology and software development.

Note: I've recently ported the content from my old blog hosted on Google App Engine using some custom code I wrote, to a static site built using Pelican. I've put in place various URL manipulation rules in the webserver config to try to support the old URLs, but it's likely that I've missed some (probably meta ones related to pagination or tagging), so apologies for any 404 errors that you get served.

RSS icon, courtesy of RSS feed for this blog

About the author

I'm a software developer who's worked with a variety of platforms and technologies over the past couple of decades, but for the past 7 or so years I've focussed on web development. Whilst I've always nominally been a "full-stack" developer, I feel more attachment to the back-end side of things.

I'm a web developer for a London-based equities exchange. I've worked at organizations such as News Corporation and Google and BATS Global Markets. Projects I've been involved in have been covered in outlets such as The Guardian, The Telegraph, the Financial Times, The Register and TechCrunch.

Twitter | LinkedIn | GitHub | My CV | Mail

Popular tags

Other sites I've built or been involved with


Most of these have changed quite a bit since my involvement in them...