We build collaboration tools every day, so we know the frustration that hits when a simple “Add comment” button balloons into a months-long engineering sprint. You want comments that blend with your brand, fit your workflow, and grow with your traffic, and you want them next sprint, not next year. The good news: a modern commenting SDK lets you get there in minutes while still handing you the paintbrush.

TLDR:

• A commenting SDK delivers both the UI components and live data infrastructure in one package, while a comment API is only the backend.

• Real customization goes far beyond color tokens; you can swap layouts, add custom fields, and wire comment events to your own services.

• Velt stands out because it gives you headless hooks, template variables, data self-hosting, and usage limits that rarely need an upgrade.

• The true cost of a comment feature includes build time, rewrites, and support; Velt cuts those by handing you ten lines of install code and Slack support.

• Follow the step-by-step example later in this post to drop inline threads on a task detail view, add a “resolved” flag, and hook notifications to Slack in under an hour.

Comment SDK vs Comment API

A comment API gives you endpoints to create, read, update, and delete comments. That is handy, but it leaves you holding the bag for the entire UI. That doesn't just mean comment boxes, mention pickers, presence indicators, reactions, and a whole lot more.

A full SDK ships those layers together so you:

• Drop ten lines of code for both the backend and frontend.

• Avoid growing maintenance & refactors costs.

• Have a starting point to build off of for the rest of our collaboration features.

Why Theme-Only Controls Are Not Enough

You can slap your brand colors on many widgets, but that is not the same as owning the experience. Teams often ask for:

• Comment threads in a sidebar on desktop but popovers on mobile.

• Extra fields such as “severity,” “story points,” or “customer impact.”

• Conditional buttons that only appear for admins.

• Special triggers: post a comment and automatically create a Jira task.

• Advanced data rules: comments on a draft visible to a private review group only.

If a vendor only mentions “matching your brand” in their docs, expect to hit hard limits once you attempt to implement any custom logic or new layouts. A true commenting SDK makes all of those requests routine. Below we cover each layer you may want to bend.

Customization Blueprint

1. Visual style

• Tokens: colors, fonts, border radius, shadows.

• CSS overrides: inject your global stylesheets or utility classes.

• Dark and light schemes.

2. Layout

• Choose sidebar, popover, inline, or your own container.

• Reorder sub-components: move avatars to the left, composer to the top, reactions below.

• Hide parts you do not need.

3. Data model

• Attach custom metadata to each comment: status, tags, assignee.

• Display that metadata in templates with simple placeholders.

• Filter or sort threads by any custom field.

4. Conditional UI

• Show a “Resolve” button only when currentUser.role === 'admin'.

• Turn comments red when comment.status === 'urgent'.

• Lock threads after a document passes a workflow step.

5. Custom actions

• “Convert to Support Ticket” button calls your REST endpoint.

• “Jump to Figma” link opens the exact frame linked in the comment.

6. Notifications

• Toggle built-in email pings on or off.

• Use webhooks to send events to Slack or Microsoft Teams.

• Build your own toast system while the SDK still handles grouping and unread counts.

The list above shows how much power you should expect before you commit. Let’s see what that looks like in a real product.

Why Velt is Easiest to Customize

We're a little biased, but we think Velt is the best commenting SDK for anybody who needs a real customization.

Many comment modes in one bundle

Just toggle a component prop and mix area pins, text highlighting, spreadsheet cell bubbles, video timeline notes in one document, one library, and one bill.

Wireframes: rebuild the UI without rebuilding the sync layer

Every UI part (thread header, composer, reaction row) is a small React or Web component you can import, reorder, or replace. Need the composer above messages? Wrap the provided parts in your own JSX and keep the real-time plumbing. You can check out our wireframe documentation to get a more detailed explanation of everything.

<VeltWireframe>
    <VeltCommentDialogWireframe.Header>
        <div className="custom-header">
            <VeltCommentDialogWireframe.Status />
            <VeltCommentDialogWireframe.Priority />
            <VeltCommentDialogWireframe.Options />
            <VeltCommentDialogWireframe.CopyLink />
            <VeltCommentDialogWireframe.ResolveButton />
        </div>
    </VeltCommentDialogWireframe.Header>
</VeltWireframe>

No fork, no copy-paste, just rearrange.

Template variables

Insert any field, built-in or custom, right in the markup:

<VeltData field="comment.priority" />
<VeltData field="comment.department"

Now, your UI shows “priority: High” or “department: Finance” without extra queries.

Conditional Templates

With Conditional Templates, you can easily show or hide different parts of your Velt Component Wireframes. It works just like Template Variables...you can set up conditions using simple syntax.

<VeltIf condition="{annotation.status.id} === 'OPEN' && {annotation.comments.length} === 3">
  {/* Content to render if condition is true */}
</VeltIf>

Action Components

This customizable button component lets you add your own actions and make any Velt component work just how you want it to.

Want to add custom filters, sorting, or grouping to your Comment Sidebar? No problem. Need special actions in your Notifications panel or Comment Dialog? You can do that too.

First we tag the component:

<VeltButtonWireframe id="close-sidebar" type="button">
     <div className="custom-button">Close Sidebar</div>
</VeltButtonWireframe

Then we create a handler:

// Hook
const veltButtonClickEventData = useVeltEventCallback('veltButtonClick');
useEffect(() => {
  if (veltButtonClickEventData) {
    if (veltButtonClickEventData.buttonContext.clickedButtonId === 'close-sidebar') {
      // Close sidebar
    }
  }
}, [veltButtonClickEventData]);

// API Method
client.on('veltButtonClick').subscribe(veltButtonClickEventData => {
  if (veltButtonClickEventData) {
    if (veltButtonClickEventData.buttonContext.clickedButtonId === 'close-sidebar') {
      // Close sidebar
    }
  }
});

Localization

For all the strings that are shown in our UI, you can set your own localization strategy through a simple mapping.

{
  "es: {
    "Yes": "Si",
    "No": "No",
    ...
  },
  "some other language code...: {
    "original string 1": "translated string 1",
    "original string 2": "translated string 2",
    ...
  },
  ...
}

Quick Tip: Use ChatGPT or Claude to generate these mappings for you.

Self-hosting, if you need it

Velt lets you keep full control of your comment and attachment data by self-hosting it on your own infrastructure (AWS, Azure, GCP, etc.), while still unlocking real-time collaboration and UI magic through their components. Your data, your rules, with no trade-off in user experience.

Beyond Styling: Workflows, Triggers, and Headless Mode

You can always check out our quickstart guide to get things started. Once you mess around with basic customzation methods, here are a few extra ideas:

• Drive a kanban board: subscribe to comment events, push “ready” items into a column.

• Anonymize comments in user tests: hide author display when testMode === true.

• Create analytics: send comment read events to your data warehouse.

• Merge voice huddles: call VeltHuddle.start() when two collaborators open the same document.

Because Velt splits logic and display, you can do all of that without touching the core sync layer.

Frequently Asked Questions

Can I drop Velt into Vue, Svelte, or plain JavaScript?
Yes. The core client is framework-agnostic. We have a React SDK and then a vanilla JavaScript client SDK that uses Web Components.

Will I lose my custom work if Velt ships a new version?
Updates are backward compatible. If you replaced parts with your own code, they keep working because you depend on stable data hooks, not private internals.

What if I outgrow the starter plan?
Most teams never get close to the starter limits which covers 200 million comments and 2TB of data. There's no need to count anymore. If you do, talk to the Velt team. Pricing for high usage is straightforward and far lower than running your own. We actually did a full build versus buy guide for commenting SDKs a little while back.

Final Thoughts

Velt proves that flexibility and short implementation time aren't mutually exclusive. From color tokens to headless mode, from webhooks to conditonal UI, every layer is open to you. Your designers get pixels that match the brand, your engineers keep their sanity, and your users get a rich thread experience that grows with them.

Ready to move comments from “someday” to “done”? Start building commenting with Velt and give your users a collaboration space that feels built just for them.