Microsoft Edge - 2026 web platform top developer needs

• <img sizes="auto" loading="lazy">

  Edge 126

  Chrome 126

  Firefox ✕

  Safari ✕

  The sizes="auto" attribute for the <img> HTML element sets the layout size for the image based on the computed layout size when choosing a source from the srcset. This attribute only applies to images with the loading="lazy" attribute.

  More information

  Developer signals and feedback

  • The feature is on Shopify's top requested features for Interop 2026, and they have created a polyfill for it (source).
  • The sizes=auto attribute is used by WordPress to improve image lazy loading (source).

  Specifications

  • https://html.spec.whatwg.org/multipage/images.html#valdef-sizes-auto

  Test results

  Number of passed subtests for <img sizes="auto" loading="lazy">. Test results from wpt.fyi. View the latest results for this feature.

• calc-size() and interpolate-size()

  Edge 129

  Chrome 129

  Firefox ✕

  Safari ✕

  The calc-size() CSS function computes mathematical expressions that include height and width keyword values, for example calc-size(fit-content, size / 2). Not to be confused with the calc() CSS function, which cannot use keyword values.
  The interpolate-size CSS property sets whether animations and transitions interpolate between a numeric value and a keyword value, such as from a fixed length to auto or fit-content.

  More information

  Developer signals and feedback

  • Animating to and from auto heights is a very common use case in CSS. This feature makes it possible to animate between a fixed length and any other type of length which can be expressed in CSS. The Interop 2025 feature proposal received 67 positive reactions on GitHub (source).
  • calc-size was the 2nd most saved reading-list item in State of CSS 2025 survey (source).
  • The webkit's standards-position issue for these features has more than 100 positive reactions (source).
  • Developer upvotes and use cases demonstrate strong demand for animating to/from auto sizes in CSS (source).

  Specifications

  • https://drafts.csswg.org/css-values-5/#calc-size
  • https://drafts.csswg.org/css-values-5/#interpolate-size

  Test results

  Number of passed subtests for calc-size() and interpolate-size(). Test results from wpt.fyi. View the latest results for this feature.

• Core Web Vitals: CLS and LoAF

  Edge 123

  Chrome 123

  Firefox ✕

  Safari ✕

  The layout-shift performance entry and LayoutShift API measures the layout stability of web pages based on movements of the elements on the page. They're used to calculate Cumulative Layout Shift (CLS), a common metric for perceived stability.
  The long-animation-frame performance event type and the PerformanceLongAnimationFrameTiming API provide information about rendering updates that take longer than 50 milliseconds. Also known as LoAFs.

  More information

  Developer signals and feedback

  • The results to the State of HTML 2025 survey indicate that developers very often run into issues that can be measured using Core Web Vitals metrics, particularly Cumulative Layout Shift (CLS) (source).
  • Cummulative Layout Shift and Long Animation Frames are part of RUMVision's Interop 2026 top requested features (source).
  • Cummulative Layout Shift and Long Animation Frames are also part of Shopify's Interop 2026 top requested features (source).

  Specifications

  • https://wicg.github.io/layout-instability/
  • https://w3c.github.io/long-animation-frames/

  Test results

  Number of passed subtests for Core Web Vitals: CLS and LoAF. Test results from wpt.fyi. View the latest results for this feature.

• corner-shape

  Edge 139

  Chrome 139

  Firefox ✕

  Safari ✕

  The corner-shape CSS property sets the shape of an element's corners when using border-radius, allowing for shapes other than rounded corners. For example, corner-shape: squircle is a shape in between a square and rounded corner.

  More information

  Developer signals and feedback

  • The Interop 2026 feature proposal received more than 90 positive reactions (source).
  • The developer signals issue about corner-shape has received more than 50 votes (source).

  Specifications

  • https://drafts.csswg.org/css-borders-4/#corner-shaping

  Test results

  Number of passed subtests for corner-shape. Test results from wpt.fyi. View the latest results for this feature.

• CSS module scripts

  Edge 123

  Chrome 123

  Firefox 147

  Safari ✕

  CSS module scripts can be loaded as constructable stylesheets by using import … with { type: "css" } statements.

  More information

  Developer signals and feedback

  • Many JavaScript frameworks and libraries have explored this space, showing a clear need for CSS modules.
  • The GitHub issue which initially introduced the CSS module scripts idea received more than 200 positive reactions (source).
  • Recent positive sentiment from developers, see A Nice Vanilla App Architecture Using Web Components and CSS Module Scripts, by Chris Coyer.

  Specifications

  • https://html.spec.whatwg.org/multipage/webappapis.html#css-module-script

  Test results

  Number of passed subtests for CSS module scripts. Test results from wpt.fyi. View the latest results for this feature.

• Customizable <select>

  Edge 135

  Chrome 135

  Firefox ✕

  Safari ✕

  The <select> element's appearance, including the button, selected option, picker dropdown, and options, can be customized using CSS.

  More information

  Developer signals and feedback

  • In the State of HTML 2025 survey, customizable <select> was the second-most voted feature which developers are unable to use because of lack of support (source).
  • In the same survey, customizable <select> was also the most voted feature which developers are unable to use because of other reasons (source).
  • Also in the same survey, <select> was the most voted HTML element which developers struggle to style or customize (source).

  Specifications

  • https://open-ui.org/components/customizableselect/

  Test results

  Number of passed subtests for Customizable <select>. Test results from wpt.fyi. View the latest results for this feature.

• Customized built-in elements

  Edge 79

  Chrome 67

  Firefox 63

  Safari ✕

  Customized built-in elements are HTML elements that extend built-in elements using the is attribute, to add new behaviors that you define.

  More information

  Developer signals and feedback

  • In the State of HTML 2025 survey, customizing and wrapping built-in elements came up in 3rd place based on the number of times this was mentioned as a freeform pain point across the entire survey (source).
  • In the same survey, extending native elements was ranked in 4th place in a multiple-choice question about web component pain points (source).
  • Multiple polyfills have been built for customized built-in elements, showing developer interest in the feature (source).
  • Many blog posts and articles have been written in favor of customized built-ins (source).

  Specifications

  • https://html.spec.whatwg.org/multipage/custom-elements.html#customized-built-in-element

  Test results

  Number of passed subtests for Customized built-in elements. Test results from wpt.fyi. View the latest results for this feature.

• Decorators

  Edge ✕

  Chrome ✕

  Firefox ✕

  Safari ✕

  Decorators are functions called on JavaScript classes, class elements, or other JavaScript syntax forms, when they are defined.

  More information

  Developer signals and feedback

  • Out of seven TC39 proposals that were tested by the TC39 proposals Short Survey, 40% of the respondents selected Decorators as their top choice, far ahead of the other proposals. (source).

  Specifications

  • https://github.com/tc39/proposal-decorators

  Test results

  Number of passed tests for Decorators. Test results from test262.fyi.

• Federated credential management

  Edge 116

  Chrome 116

  Firefox ✕

  Safari ✕

  The IdentityCredential API delegates authentication to a third-party identity provider, instead of using third-party cookies. Also known as FedCM.

  More information

  Developer signals and feedback

  • FedCM is crucial for helping our industry move away from third-party cookies.
  • The FedCM specification repository has over 400 stars and 90 forks, showing interest in the technology (source).
  • According to Chrome's useCounters, usage of the feature is above 2% of all page loads in Chrome, despite the feature only being available in Chrome and Edge (source).
  • The feature is part of Shopify's Interop 2026 top requested features as it enables their merchants to offer personalized, one-tap sign-in experiences for their storefronts, but also improves retention and has other benefits (source).

  Specifications

  • https://w3c-fedid.github.io/FedCM/

  Test results

  Number of passed subtests for Federated credential management. Test results from wpt.fyi. View the latest results for this feature.

• field-sizing

  Edge 123

  Chrome 123

  Firefox ✕

  Safari 26.2

  The field-sizing CSS property allows form controls such as <textarea> to be sized based on their content.

  More information

  Developer signals and feedback

  • The field-sizing property was the 3rd-most popular reading list item in the State of CSS 2025 survey, showing a lot of interest from participants in learning more about it (source).
  • Styling and customization was, by far, the first response to the State of HTML 2024 question about HTML form pain points (58%), followed by Input element issues (27%), where an entire sub-category of answers is dedicated to auto-growing textareas (source).
  • The autosize NPM package, which automatically adjusts the height of textareas to fit their content, has more than 650,000 weekly downloads (source).
  • The react-textarea-autosize NPM package is downloaded 4.6M times per week (source).

  Specifications

  • https://drafts.csswg.org/css-forms-1/#field-sizing

  Test results

  Number of passed subtests for field-sizing. Test results from wpt.fyi. View the latest results for this feature.

• Intersection observer visibility tracking

  Edge 79

  Chrome 74

  Firefox ✕

  Safari ✕

  The trackVisibility parameter for the IntersectionObserver constructor enables tracking the visibility of an element, to detect if it may be obscured by other content or visual effects. Also known as IntersectionObserver v2.

  More information

  Developer signals and feedback

  • In the 2022 APIs and JavaScript MDN short survey, more than 15% of respondents agreed that the Intersection Observer API needed to be improved across browsers (source).
  • According to Chrome's useCounters, usage of the feature is above 9% of all page loads in Chrome (source).

  Specifications

  • https://w3c.github.io/IntersectionObserver/#calculate-visibility-algo

  Test results

  Number of passed subtests for Intersection observer visibility tracking. Test results from wpt.fyi. View the latest results for this feature.

• JPEG XL

  Edge ✕

  Chrome ✕

  Firefox ✕

  Safari 17

  The JPEG XL image format is a raster graphics file format that supports animation, alpha transparency, and lossy as well as lossless compression.

  More information

  Developer signals and feedback

  • The proposal to include JPEG XL in Interop 2026 received more than 500 positive reactions (source).
  • The JPEG XL developer signals issue has more than 400 positive reactions (source).
  • The Chromium issue about adding JPEG XL support in Blink has more than 1000 upvotes (source).

  Specifications

  • https://www.iso.org/standard/85253.html

  Test results

  Number of passed subtests for JPEG XL. Test results from wpt.fyi. View the latest results for this feature.

• justify-self in block layouts

  Edge 130

  Chrome 130

  Firefox ✕

  Safari ✕

  The justify-self CSS property aligns an item along a container's inline axis in block layouts, like it does in grid layouts. Likewise, the justify-items property sets a default justify-self value for all items in a container in a block layout.

  More information

  Developer signals and feedback

  • Major sites have started relying on this feature, causing web compatibility issues in non-supporting browsers (source).
  • The proposal for the inclusion of this feature in Interop 2026 received more than 20 positive reactions (source).

  Specifications

  • https://drafts.csswg.org/css-align-3/#justify-block

  Test results

  Number of passed subtests for justify-self in block layouts. Test results from wpt.fyi. View the latest results for this feature.

• moveBefore()

  Edge 133

  Chrome 133

  Firefox 144

  Safari ✕

  The moveBefore() DOM method relocates a node while preserving its state. For example, you can move the active element without losing focus, move an animated element without resetting the animation, or move an iframe without reloading its content.

  More information

  Developer signals and feedback

  • The Microsoft Office online team shared their strong interest for this feature (source).

  Specifications

  • https://dom.spec.whatwg.org/#dom-parentnode-movebefore
  • https://html.spec.whatwg.org/multipage/custom-elements.html#preserving-custom-element-state-when-moved

  Test results

  Number of passed subtests for moveBefore(). Test results from wpt.fyi. View the latest results for this feature.

• reading-flow

  Edge 137

  Chrome 137

  Firefox ✕

  Safari ✕

  The reading-flow CSS property sets the order in which flex or grid elements are rendered to speech or reached via focus navigation. The reading-order property overrides this order.

  More information

  Developer signals and feedback

  • The impact of changing the visual order of items in a layout, in a way that's disconnected from the tabbing/source order has been documented extensively over the years, showing that the reading-flow property solves a real problem.
  • See The order property and accessibility, on MDN.
  • See Flexbox & the keyboard navigation disconnect, by Léonie Watson.
  • See HTML Source Order vs CSS Display Order, by Adrian Roselli.
  • See Solving the CSS layout and source order disconnect, by Rachel Andrew.

  Specifications

  • https://drafts.csswg.org/css-display-4/#reading-flow

  Test results

  Number of passed subtests for reading-flow. Test results from wpt.fyi. View the latest results for this feature.

• requestIdleCallback()

  Edge 79

  Chrome 47

  Firefox 55

  Safari ✕

  The requestIdleCallback() API queues a function that runs in idle browser time, either at the end of a frame or when the user is inactive. Also known as the background tasks API.

  More information

  Developer signals and feedback

  • The requestIdleCallback shim is downloaded 520,000 times per week on NPM (source).
  • Chrome's useCounters report that the method is used on 45% of page loads in Chrome (source).
  • The feature is part of RUMVision's Interop 2026 top requested features, because it helps keep the main thread free, reducing input blocking and jank (source).

  Specifications

  • https://w3c.github.io/requestidlecallback/

  Test results

  Number of passed subtests for requestIdleCallback(). Test results from wpt.fyi. View the latest results for this feature.

• Scheduler API

  Edge 129

  Chrome 129

  Firefox 142

  Safari ✕

  The scheduler API provides a way to prioritize all tasks belonging to an application.

  More information

  Developer signals and feedback

  • Chrome's useCounters report a usage that's above 10% of all page loads in Chrome, and growing, even though the feature isn't yet supported in all major browsers (source).

  Specifications

  • https://wicg.github.io/scheduling-apis/

  Test results

  Number of passed subtests for Scheduler API. Test results from wpt.fyi. View the latest results for this feature.

• sibling-count() and sibling-index()

  Edge 138

  Chrome 138

  Firefox ✕

  Safari 26.2

  The sibling-count() and sibling-index() CSS functions return integers that are useful to style elements based on their positions among siblings or on the number of siblings, for example as part of a calc() expression.

  More information

  Developer signals and feedback

  • The sibling-count() and sibling-index() functions were the 11th and 13th most-saved reading list items in the State of CSS 2025 survey (source).
  • The developer signals issue about sibling-count and sibling-index has received more than 60 votes (source).

  Specifications

  • https://drafts.csswg.org/css-values-5/#tree-counting

  Test results

  Number of passed subtests for sibling-count() and sibling-index(). Test results from wpt.fyi. View the latest results for this feature.

• Speculation rules

  Edge 109

  Chrome 109

  Firefox ✕

  Safari ✕

  Speculation rules are hints to the browser to proactively download pages in the background so they appear instantly when the user navigates to them.

  More information

  Developer signals and feedback

  • According to Chrome's useCounters, Speculation Rules prefetches are used on more than 10% of page loads in Chrome, and growing (source).
  • The google.com search results page uses Speculation Rules to prefetch links (source).
  • WordPress 6.8 uses speculation rules to improve performance (source).
  • The feature is part of RUMVision's Interop 2026 top requested features, because it speeds up the user-perceived navigation time without relying on heavy JavaScript (source).
  • The feature is also part of Shopify's Interop 2026 top requested features. They deployed the feature across all merchant storefronts and observed significant benefits, such as 130ms to 180ms improvements in same-origin navigation across all loading metrics and all percentiles (source).

  Specifications

  • https://html.spec.whatwg.org/multipage/speculative-loading.html#speculation-rules
  • https://wicg.github.io/nav-speculation/prerendering.html

  Test results

  Number of passed subtests for Speculation rules. Test results from wpt.fyi. View the latest results for this feature.

• Temporal

  Edge 144

  Chrome 144

  Firefox 139

  Safari ✕

  The Temporal API allows you to work with dates, times, time zones, and durations. It is more powerful than the Date API.

  More information

  Developer signals and feedback

  • The feature gathered a lot of positive developer signals (source).
  • Moment.js, the de-factor standard library to parse, validate, manipulate, and format dates, is downloaded nearly 28,000,000 times per week on MPM (source).
  • In the State of JS 2025 survey, Temporal is the most wished-for JavaScript proposal (source).

  Specifications

  • https://tc39.es/proposal-temporal/

  Test results

  Number of passed tests for Temporal. Test results from test262.fyi.

• text-wrap: pretty

  Edge 117

  Chrome 117

  Firefox ✕

  Safari 26

  The text-wrap: pretty CSS declaration prioritizes better layout over speed when text is broken into multiple lines.

  More information

  Developer signals and feedback

  • text-wrap:pretty is already used on more than 1.5% of all page loads in Chrome and growing, according to Chrome's useCounters (source).
  • The CSS property received positive developer sentiment (source).

  Specifications

  • https://drafts.csswg.org/css-text-4/#valdef-text-wrap-style-pretty

  Test results

  Number of passed subtests for text-wrap: pretty. Test results from wpt.fyi. View the latest results for this feature.

• Trusted types

  Edge 83

  Chrome 83

  Firefox 148

  Safari 26

  Trusted types allow you to lock down insecure parts of the DOM API and prevent client-side cross-site scripting (XSS) attacks.

  More information

  Developer signals and feedback

  • According to Chrome's useCounters, Trusted Types policies are created in more than 65% of page loads in Chrome (source).
  • Salesforce strongly supports the feature (source).
  • The integration of Trusted Types is either completed or ongoing in several libraries and frameworks (source).
  • Interest from the community and adoption on supporting browsers is high (source).

  Specifications

  • https://w3c.github.io/trusted-types/dist/spec/

  Test results

  Number of passed subtests for Trusted types. Test results from wpt.fyi. View the latest results for this feature.

• Virtual keyboard

  Edge 94

  Chrome 94

  Firefox ✕

  Safari ✕

  The navigator.virtualKeyboard API inspects and controls on-screen virtual keyboards. You can use it to programmatically hide or show a virtual keyboard or respond to the keyboard disappearing or appearing.

  More information

  Developer signals and feedback

  • The Virtual Keyboard API solves a common developer problem that's illustrated by the existence of many questions related to detecting the on-screen keyboard on StackOverflow (source).
  • Ahmad Shadeed described the problem and how the VirtualKeyboard API solves it in a detailed article (source).

  Specifications

  • https://w3c.github.io/virtual-keyboard/

  Test results

  Number of passed subtests for Virtual keyboard. Test results from wpt.fyi. View the latest results for this feature.

• Web Bluetooth

  Edge 79

  Chrome 70

  Firefox ✕

  Safari ✕

  The Web Bluetooth API enables selecting and communicating with nearby Bluetooth devices.

  More information

  Developer signals and feedback

  • In the State of HTML 2025 survey, the 2nd-most voted system capabilities-related pain point was related to specific platform APIs and capabilities, which includes Web Bluetooth (source).
  • Production sites have started to use Web Bluetooth, causing web compatibility issues in non-supporting browsers (source).
  • The Espruino project has now shipped over 50,000 devices, which their customers are relying on Web Bluetooth to communicate with (source).

  Specifications

  • https://webbluetoothcg.github.io/web-bluetooth/

  Test results

  Number of passed subtests for Web Bluetooth. Test results from wpt.fyi. View the latest results for this feature.

  Tests are failing for Chrome in the graph above because Chrome is tested by WPT on Linux and the Web Bluetooth feature isn't currently enabled on Chrome for Linux.

• WebDriver BiDi

  Edge 106

  Chrome 106

  Firefox 102

  Safari ✕

  WebDriver BiDi is a bidirectional protocol that allows a WebDriver client and a browser to communicate with each other.

  More information

  Developer signals and feedback

  • The Interop 2025 feature proposal for WebDriver BiDi received more than 70 positive reactions (source).
  • Industry-wide surveys such as the MDN Web Developer Needs Assessment and the MDN Web Testing Report have identified cross-browser testing as one of the top developer pain points.

  Specifications

  • https://w3c.github.io/webdriver-bidi/

  Test results

  Number of passed subtests for WebDriver BiDi. Test results from wpt.fyi. View the latest results for this feature.