Web Compatibility issues change over time. Bugs that were common in 2005 are not often seen in the present. This list represents the most common issues currently being discovered by the webcompat community and will be updated as these change in the future.
The Mozilla Bugzilla issues have a WebCompat priority flag from P1 to P3 following a triage process.
Summary
Current Popular Issues
(This needs to be adjusted @@karl 2020-10-20)
Bugzilla WebCompat Core Bug
Full Query
ID |
Summary |
Priority |
Status |
91370 |
Implement setting cssText on various CSSRule implementations |
P3 |
NEW |
102695 |
[EVENTTARG]Treat some transparent elements as "transparent to events" |
P3 |
NEW |
129432 |
'onkeypress', 'onkeydown', onkeyup' not working on FORM,LEGEND,OPTGROUP,OPTION |
-- |
NEW |
137687 |
Computed CSSDeclarations need to implement GetCssText |
P3 |
NEW |
406488 |
Copy highlighted text to clipboard ignores non-inlined CSS styling when pasting as rich text (to HTML editors, MS Word, Excel, Outlook etc.) |
-- |
NEW |
662496 |
autofocus not work when the element is added to the DOM after the document is done loading (e.g. in window.onload) |
-- |
NEW |
695868 |
Unable to set document.body.innerHTML of IFrame |
P3 |
NEW |
997189 |
Absolutely positioned inline-block (or inline) element with floating nextSibling and auto "left" is positioned to the right of the float |
-- |
NEW |
1034018 |
outline: auto is not applied in the same way as it is on blink |
P3 |
NEW |
1039871 |
Add support to HTML media element for determining the mimetype of a loaded media file |
-- |
NEW |
1043118 |
Do not select leading/trailing spaces on double clicking. |
P3 |
NEW |
1199665 |
Consider making <input type=number> always fall back to parsing numbers as English formatted numbers if parsing them as numbers formatted using the user's locale fails |
-- |
ASSIGNED |
1248570 |
Firefox can't play wav in video or audio element |
P3 |
NEW |
1273010 |
Blocky and slow rendering on Firefox Android Nightly - filter: drop-shadow() |
P3 |
ASSIGNED |
1274354 |
[meta] Date.parse, amirite |
P3 |
NEW |
1307024 |
[Perf] [google docs] Firefox will get 3~9% faster when running gdoc test cases with chrome user agent |
-- |
NEW |
1307678 |
Title of latest recommendation of language.chinadaily.com.cn is cut |
P3 |
NEW |
1322694 |
WebGL video textures fail to render in Firefox Nightly for MP4 format with 2048x1024 pixels dimensions |
P3 |
UNCONFIRMED |
1336245 |
Geolocation should return available low-res location when high-res location is not yet available |
P2 |
NEW |
1337114 |
Diacritics rendered incorrectly with decomposed unicode and Proxima Nova |
P3 |
NEW |
1342569 |
mouseenter/mouseleave fire differently on <select>s in e10s mode. |
P2 |
NEW |
1353248 |
[e10s] select - options styling doesn't work properly if CSS selector :-moz-focusring is present |
P3 |
NEW |
1360238 |
window.getSelection().toString() displays extra "\n" characters on multiple block elements, even if they are display:inline |
P3 |
NEW |
1362499 |
Support unit-less values for CSS -webkit-perspective (for interop) |
P3 |
NEW |
1362898 |
content with ::before gets painted at the wrong place |
-- |
NEW |
1376369 |
-moz-user-select:none triggers dragging also when @draggable="false" |
P3 |
NEW |
1382471 |
Firefox wraps word-broken text under a previous float-left, rather than starting it on the same line. |
P3 |
NEW |
1385382 |
bullet with text-align:center is positioned further to the right in Firefox, as compared to other browsers (breaking fake radio button at wetter.7pass.de) |
P3 |
NEW |
1385419 |
Parent element stretches to submit input's line-height, rather than its also-specified height. |
P3 |
NEW |
1411862 |
Disable 3rd party cookie video does not play in Firefox Dev Edition (v57 with uBlockO). |
P3 |
NEW |
1414402 |
Support playback of mp4v video |
P5 |
NEW |
1417753 |
Implement -moz-appearance: searchfield-cancel-button which behave like -webkit-appearance: searchfield-cancel-button |
P3 |
NEW |
1421597 |
Provide an option to ignore scroll events outside of the control when a |select| drop-down is open |
P3 |
NEW |
1422891 |
[Rethink] Support mkv|matroska|video/x-matroska in Firefox |
P3 |
UNCONFIRMED |
1436801 |
Vertical border and padding influences alignment of text in spans with "vertical-align:middle" (only in Firefox) |
P3 |
NEW |
1437761 |
position:sticky inside partially-offscreen position:fixed container has a different behavior in Chrome/Edge vs Firefox |
P3 |
NEW |
1438398 |
After opening then closing the Account panel (top-right blue-ish icon), the page doesn't reflow correctly. |
P3 |
NEW |
1443284 |
percentage height in auto-height table cell in fixed-height table is treated as auto |
P3 |
NEW |
1447524 |
Double session history entries from https://www.microsoft.com/en-us/news |
P2 |
NEW |
1449079 |
PNG background-image icon not positioned at the right place after first rendering |
P3 |
NEW |
1450815 |
HTTP POST receives a response with a onload event in JS posting to itself and generating an infinite loop |
P3 |
NEW |
1451998 |
the thumbnails all play automatically at the same time, and the website gets so slow it's impossible to use. |
P3 |
NEW |
1452646 |
while clicking and navigating back, an outline is drawn |
P3 |
NEW |
1453797 |
Carousel images have jagged edges when scrolling through |
P3 |
NEW |
1454043 |
Carousel images have jagged edges when scrolling through |
P3 |
NEW |
1455545 |
Noto Sans Symbols is not rendered on some Android devices |
P3 |
NEW |
1459535 |
Performance is incredibly degraded when idle on Foreignpolicy.com |
P3 |
NEW |
1461266 |
comments framerate is smoother on Chrome than Firefox |
P3 |
NEW |
1463335 |
anchor and input superposed makes the JavaScript non active. |
P3 |
NEW |
1464925 |
Visual glitch: graphic layers around menu displaced, linked to scroll position. |
P3 |
NEW |
1467114 |
BBC - highlighter for navigation spans extends to body edge |
P3 |
NEW |
1471232 |
iframe content overflow spontaneously after a couple of seconds |
P2 |
REOPENED |
1473501 |
Improve the way Gecko selects images based on srcset values (don't just round up, when rounding up is a huge jump) |
P3 |
NEW |
1475681 |
Page CSP can break seeking to unbuffered position (in mp3 playback) |
P3 |
REOPENED |
1475723 |
Geckoview and Fennec open select dropdown on tap of parent label; other browsers do not. |
P3 |
NEW |
1476051 |
Interop issues with select element styling with appearance:none. |
P3 |
NEW |
1477110 |
Select elements seem to get double the text-indent |
P3 |
NEW |
1481132 |
[Android] businessinsider.com flashes 3 times when you reload or navigate away |
P3 |
NEW |
1481581 |
[meta] More closely align the behavior of '-moz-appearance' with Chrome's '-webkit-appearance' |
P3 |
NEW |
1481596 |
Make `-moz-appearance: none` on <textarea> behave more like Chrome |
P3 |
NEW |
1486365 |
The City selection page slightly bounces after opening |
P3 |
NEW |
1490873 |
Toggling SVG graph elements on and off leaves artifacts and erases parts. |
P3 |
NEW |
1491743 |
invalid CSS property value on ::selection kills the default selection settings |
P3 |
NEW |
1493434 |
Inconsistent table column sizing between Firefox and Chrome (with percent sizes on colgroup and col) |
P3 |
NEW |
1495868 |
Unprefix -moz-available keyword |
P3 |
NEW |
1499986 |
Handling javascript URL returning a non-string value |
P3 |
NEW |
1501480 |
mask-image and SVG on input element fails in Firefox, Safari, and Edge, works in Chrome |
P3 |
NEW |
1503427 |
Firefox 63 pushing Bootstrap 3 date input text down |
P3 |
NEW |
1503899 |
Sharp printer UI incorrectly rendered, due to table-layout behavior difference (& with CSS enabled by webkit-min-device-pixel-ratio query) |
P3 |
NEW |
1506487 |
m.acfun.cn - video not playing, OS needs to be restarted. |
P3 |
NEW |
1513435 |
Incompatible column layout with 'height:0' and definite 'column-width' |
P3 |
UNCONFIRMED |
1514269 |
[CSS Multicol] Firefox only web platform tests |
P2 |
NEW |
1514362 |
[CSS Selectors] Firefox only web platform test failures |
P3 |
NEW |
1514371 |
[CSSOM] Firefox only web platform test failures |
P2 |
NEW |
1517666 |
quick zoom in and out will white out Firefox and all tabs |
P3 |
NEW |
1518040 |
SVG feBlend should take account of flood-opacity on feFlood input nodes |
P3 |
NEW |
1522706 |
History.pushState limit may be too low for some live sites |
P3 |
NEW |
1523231 |
Screen problems not everything is there |
P3 |
NEW |
1529471 |
objectBoundingBox, clip-path behave differently in Chrome and Firefox |
P3 |
NEW |
1530577 |
(Un)Expected HTTPS upgrade of download due to <meta ... "upgrade-insecure-requests"> tag |
P3 |
NEW |
1532481 |
Firefox does not expand certain list items so they do not vertically overlap, as other engines do. |
P3 |
NEW |
1541330 |
Speech Synthesis play incorrect |
P3 |
NEW |
1542995 |
Thousands of window.onload events creates high memory/CPU until it crashes |
P3 |
NEW |
1543059 |
Loading spinner displays at end of some non-looping videos hosted on reddit.com |
P3 |
NEW |
1545703 |
images.google.com - Some videos do not play or play erratically |
P3 |
NEW |
1548376 |
Flickering videos when scrolling on Buzzfeed |
P3 |
NEW |
1550158 |
Blink and Gecko differ on where to flow absolutely-positioned element in a tight layout |
P4 |
UNCONFIRMED |
1577904 |
Interop differences in iframe html/body offsetHeights as reported by Chrome and Firefox |
-- |
NEW |
1656279 |
Unitless line height interop issue |
-- |
NEW |
89 Total;
89 Open (100%);
0 Resolved (0%);
0 Verified (0%);
FIXED
This is the Yeah! Let's party list.
WebKit Flexbox Total Armaggedon in China and Japan
This is not specific to Desktop and Mobile, but more to the specific markets of China and Japan and indeed more often on mobile.
Suggested Fix
Use Web standards flexbox properties in addition to the WebKit ones if old devices compatibility is required.
Related Bugs
Click-or-touch
Many sites have code that detects touch support and assumes mouse input can be ignored. These sites behave oddly on all computers that have a touch screen AND a mouse - usually not responding as expected to mouse input.
Suggested Fix
Write JavaScript that will handle both click and touch input, not either-or.
Related Bugs
Max-width
(Fixed in Gecko)
Basically an image with a max-width: 100% was bigger than the viewport
It was an issue, created by a different behavior in Gecko and Blink. But the market share of Blink imposed the unspecc’ed behavior of Blink.
Suggested Fix
The fix was often a combination of display: table with table-layout: fixed.
This is now fixed in Gecko and the spec, but this is a good illustration point in terms of Web Compatbility issues.
Related Bugs
Video streaming using Apple’s proprietary HTTP Live Streaming
Firefox doesn’t support this on Desktop or Mobile.
Suggested Fix
Not a trivial thing to fix. Ensure that there is a fallback mechanism for browsers that don’t support HLS (currently on Desktop, only Edge and Safari do).
Related Bugs
Meta viewport fixed size
Very similar to the max-width bug. This is a different of behavior in between blink and Gecko.
Basically with a fix width, Gecko on Mobile doesn’t necessary resize the page to fit in the screen.
Suggested Fix
Use width=device-width instead of fixed size.
Related Bugs
Faulty UA detection
Sites sniff the user agent string, often to figure out if you’re using a “supported browser”. This goes wrong all the time, because of an unknown UA string, or parsing bugs, or not understanding versions greater than 9, etc. Mobile browsers will frequently end up on “Desktop” sites, rather than mobile ones as a result of this kind of bug.
Suggested Fix
Update your UA detection library or framework, or use feature detection rather than relying on User Agent string parsing. User Agent detection is about detecting the past. So it will obviously fail. Feature detection is about inspecting the now.
Related Bugs
Relying on global event object
WebKit (possibly copied from old iE?) has a non-standard global event object. When sites don’t pass in the event object to an event handler, we end up with exceptions like “ReferenceError: event is not defined”
Suggested Fix
Use web standards and pass in an explicit event object into your event handlers.
For example:
a.addEventListener(‘click’, function(e){ blah(e)});
Related Bugs
HTTP Ping Pong
The company has two different sites: desktop and mobile with different domain names. They do user-agent sniffing be with HTTP user-agent header, through JavaScript.
Suggested Fix
The issue starts to fix itself by people switching to responsive Web sites.
The fix is actually simple. Which ever technique you are using should have a consistent policy in terms of user agent sniffing.
Some websites make mistakes when the detection mechanism is not the same on both domains: for example one with HTTP, and one with JS. In HTTP only, the browser is able to identify the infinite loop and will stop after 10 iterations, but when switching from HTTP to JS and then to HTTP, etc the browser is really caught forever.
Related Bugs
Webkit Scrollbar
Websites would like to replace default scrollbars with custom ones. There are known issue of Firefox not hiding the default scrollbar and potential scrollbar lagging introduced with async scrolling (e10s-only).
Related Bugs