# Support for W3C-valid data- attributes in Finsweet Components (CMS Slider) **URL:** \ **Category:** Finsweet Components\ **Tags:** cmsslider\ **Created:** [October 11, 2026, 1:43pm UTC](https://forum.finsweet.com/t/support-for-w3c-valid-data-attributes-in-finsweet-components-cms-slider/7591 "2026-10-11T13:43:23Z")\ **Posts on this page:** 4\ **Page:** 1
**Author:** ![admin10](https://dub1.discourse-cdn.com/flex013/user_avatar/forum.finsweet.com/admin10/32/6589_2.png) [@admin10](https://forum.finsweet.com/u/admin10)\ **Post date:** [October 11, 2026, 1:43pm UTC](https://forum.finsweet.com/t/support-for-w3c-valid-data-attributes-in-finsweet-components-cms-slider/7591/1 "2026-10-11T13:43:23Z")
## **Description** We’re using Finsweet Components (CMS Slider) on a client site in Webflow. When we run the site through the W3C Markup Validator ([https://validator.w3.org/](https://validator.w3.org/)), the only errors left come from Finsweet: 1. **Slider attributes:** `fs-slider-type`, `fs-slider-instance` and `fs-slider-element` on `div` and `button` elements return “Attribute fs-slider-element not allowed on element div at this point.” (8 errors) 2. **Script injected by the Webflow app** (`componentsconfig-1.0.5.js`): `siteId="..."` and `finsweet="components"` return “Attribute siteid not allowed on element script at this point.” (2 errors) Under the HTML spec, custom attributes need the `data-` prefix to be valid. We’d like to use W3C-valid attributes like `data-fs-slider-element`, and ideally have the injected script use `data-site-id` and `data-finsweet`. Is this already supported? If not, could you consider adding it? ## **Site URL** - URL: [https://nue-gmbh.webflow.io/](https://nue-gmbh.webflow.io/) - Webflow Read-only link: [Read-only-Link einfügen] ## **Steps to Reproduce** 1. Open [https://validator.w3.org/](https://validator.w3.org/) 2. Choose “Validate by URI” and enter [https://nue-gmbh.webflow.io/](https://nue-gmbh.webflow.io/) 3. Click “Check” 4. See the errors for the `fs-slider-*` attributes and for the `siteId`/`finsweet` attributes on the components script ## **Expected Behavior** Finsweet Components work with W3C-valid markup (`data-` prefixed attributes), so the page validates without errors from Finsweet. ## **Actual Behavior** The validator returns 10 errors. All of them come from the Finsweet slider attributes and the script injected by the Finsweet Components app. Every other error on the site has been fixed. ## **Video/Screenshots** - Video link: [Loom-Link einfügen] - Screenshots: [Screenshot vom Validator-Report] ## **Additional Context** - Browser: Not browser-specific (markup validation) - Device: Not device-specific - Finsweet Components config version: 1.0.5 ---
**Author:** ![jesse.muiruri](https://dub1.discourse-cdn.com/flex013/user_avatar/forum.finsweet.com/jesse.muiruri/32/5523_2.png) [@jesse.muiruri](https://forum.finsweet.com/u/jesse.muiruri)\ **Post date:** [October 11, 2026, 5:03pm UTC](https://forum.finsweet.com/t/support-for-w3c-valid-data-attributes-in-finsweet-components-cms-slider/7591/2 "2026-10-11T17:03:59Z")
Hi @admin10, We checked the website and can see you’ve implemented a workaround for the `fs-slider-*` attributes You have them initially in Webflow as `data-fs-slider-*` so as to pass the `W3C Markup Validator` checks Then there’s custom code in there to rework them back to the required `fs-slider-*` attributes that Finsweet Components expects The only issue now, as per the `W3C Markup Validator` checks, is the remaining two attributes on the actual CDN script itself that Finsweet Components adds to the site These are the `siteId="..."` and `finsweet="components"` attributes First & foremost we need to emphasize that these `W3C Markup Validator` errors are conformance warnings about custom attribute names Browsers generally ignore any unknown attributes and so the Finsweet Component attributes will in no way affect the site rendering, or its accessibility, or site SEO You could consider documenting them as known third-party exceptions That being said, you’ve at least sorted out 8 of the validator errors with the smart workaround However, you should try test it thoroughly for potential nuances For instance, the Finsweet CDN loads `async` & so if for some reason your attribute-correction script runs while Finsweet CDN is also starting up, the slider may never be initialized & your code’s restart may also fail on the `if` check, hence no slider The `restart()` is also undocumented API & so a future release of Finsweet Components might potentially break it You would’ve to keep tabs on it perpetually A routine edit on the Slider settings could potentially re-add the `fs-slider-*` attributes without notice The [_ **docs** _](https://finsweet.com/components/slider/docs) advice against removing the attributes `Do not remove the attributes. They are required for the Slider component to work.` We can confirm that [_ **Finsweet Attributes** _](https://finsweet.com/attributes/how-finsweet-attributes-works) are `fs-` prefixed There are no `data-fs-*` aliases in the works We would suggest working with the current `fs-slider-*` attributes as is, considering they don’t affect function, accessibility or SEO Thanks ---
**Author:** ![admin10](https://dub1.discourse-cdn.com/flex013/user_avatar/forum.finsweet.com/admin10/32/6589_2.png) [@admin10](https://forum.finsweet.com/u/admin10)\ **Post date:** [October 11, 2026, 6:06pm UTC](https://forum.finsweet.com/t/support-for-w3c-valid-data-attributes-in-finsweet-components-cms-slider/7591/3 "2026-10-11T18:06:05Z")
> [@jesse.muiruri](#): > > We would suggest working with the current `fs-slider-*` attributes as is, considering they don’t affect function, accessibility or SEO Hi Jesse, Thanks for taking the time to look at the site in such detail. I really appreciate it. I understand that browsers ignore unknown attributes and that this doesn’t affect rendering, accessibility or SEO. Still, for us and our clients, valid markup is part of delivering clean, professional work. Clients run these checks, and “known third-party exceptions” are hard to explain when the HTML spec already defines a standard way to add custom attributes: the `data-` prefix. Your reply actually makes the case for native support. Every risk you pointed out comes from the workaround: - the race condition with the async CDN script - relying on the undocumented `restart()` API - slider settings that could quietly re-add the `fs-slider-*` attributes If Finsweet supported `data-` attributes natively, none of these would apply. There’d be no workaround, the validator would pass, and everything would run stable. So I’d like to ask you to consider: 1. **Accepting `data-fs-*` as an alias** for the existing `fs-*` attributes (e.g. `data-fs-slider-element`). That’s fully backward compatible, so existing projects keep working. 2. **Using `data-` attributes on the injected script** as well (e.g. `data-site-id` and `data-finsweet` instead of `siteId` and `finsweet`). Could you pass this on to the team as a feature request? I’m sure we’re not the only ones who care about valid markup. Thanks again for your help! Best regards ---
**Author:** ![jesse.muiruri](https://dub1.discourse-cdn.com/flex013/user_avatar/forum.finsweet.com/jesse.muiruri/32/5523_2.png) [@jesse.muiruri](https://forum.finsweet.com/u/jesse.muiruri)\ **Post date:** [October 11, 2026, 6:26pm UTC](https://forum.finsweet.com/t/support-for-w3c-valid-data-attributes-in-finsweet-components-cms-slider/7591/4 "2026-10-11T18:26:02Z")
Hi admin, Sure, I’ll definitely pass it on to the devs as a feature request Thanks once again for suggesting improvements to the product & the Finsweet ecosystem in general