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Optimizely Content Management System (CMS) offers some features to make client-side rendering easier. These features are framework agnostic, so you can use them with any JavaScript framework, such as Angular, React, or Vue.

## Edit HTML attributes

CMS UI provides the attribute `data-epi-edit` that can be added to editable DOM elements:


Using `data-epi-edit="YourProperty"` is equivalent to adding 3 other HTML attributes as below:

  • `data-epi-property-name="YourProperty"`
This attribute marks an element for editing.
  • `data-epi-property-render="none"`
This attribute prevents the DOM from being modified directly when editing. Using `data-epi-property-edittype="inline"` overrides this and will modify the DOM (note, "inline" is the default for string properties).
  • `data-epi-property-edittype="floating"`
This attribute creates a dialog for editing, and should be used for string types.
### Edit HTML attributes for blocks
Editable blocks rendered in a content area should have this HTML attribute on each block element:
  • `data-epi-block-id="ContentLinkID"`
This attribute marks a block element for editing.
## Re-rendering
To know when to re-render, subscribe to the topic **contentSaved**. The controller must contain the attribute` [RequireClientResources]` unless it inherits from either PageController or ContentController, as these both include the attribute by default. The resources then need to be required in a razor view with other scripts for the site `using @Html.RequiredClientResources("Footer")`.
## Handle context modes
In order to properly apply edit overlays and enable/disable client-side routing as needed, the client requires some sort of indicator of the current context mode. For this purpose, Optimizely provides the following properties in the epi object :
  • `inEditMode`
True in both edit mode and preview mode
  • `isEditable`
True in edit mode and false in preview mode
  • `ready`
True if the property `isEditable` has been initialized. Otherwise, subscribe to `epiReady` to get those properties as soon as they are available
## Navigate in on-page edit
To update the editing context (page tree, for this page folders and so on) when navigating the site by clicking links in the preview iframe there are two requirements. The links needs to be actual hyperlinks with an <a> tag and the href attribute needs to be an "edit mode" URL. Details can be found in this [blog post on routing](🔗).
## Content delivery API
CMS has released a content delivery API to make a headless implementation even easier. See [Content Delivery API](🔗).
## SPA template site
To demonstrate some useful concepts when creating a Single Page Application with working on-page editing, see [the MusicFestical SPA template site on Github](🔗). For descriptions of the template site, see the blog post [Introducing a new SPA template site: MusicFestival](🔗).
## Recommended blog series
  1. [Introducing a new SPA template site: MusicFestival](🔗)
  2. [Routing in a SPA with a working On-Page Editing experience (CMS UI 11.11.0)](🔗)
  3. [Tips and tricks for a great On-Page Editing experience in SPAs and other client side rendered sites](🔗)
  4. [Represent the concept of "pages" and "blocks" with matching client side components in a SPA](🔗)
## Blog posts
  • [Taking control of client-side rendering in OPE](🔗)
  • [Taking more control of client-side rendering in OPE](🔗)
  • ["domUpdated" is no longer needed](🔗)
  • [One OPE attribute to rule them all: data-epi-edit](🔗)
  • [Designing frontends for OPE without wrapping elements](🔗)