Content Preview

Content Preview

The Box Content Preview UI Element allows developers to embed high quality and interactive previews of Box files in their desktop or mobile web application. The library fetches information about the file and its converted representations through the Box API, chooses the appropriate viewer for the file type, dynamically loads the necessary static assets and file representations, and finally renders the file. This UI Element also allows previews of multiple files to be loaded in the same container and exposes arrows to navigate between those files.

This UI Element powers Preview in the main Box web application as well as the 'expiring embed' Box API endpoint.

Installation

Learn how to install Box UI elements either through NPM or the Box CDN.

Browser support

UI elements have limited support for older browsers. Make sure to add the right polyfills for your targeted browsers.

Authentication

The UI Elements are designed in an authentication agnostic way so whether you are using UI Elements for users who have Box accounts (Managed Users) or non-Box accounts (App Users), UI Elements should work out of the box. The reason for this is that UI Elements only expect a "token" to be passed in for authentication, and Box provides two different ways to generate tokens - OAuth and JWT.

Learn about selecting an authentication method

Supported File Types

Box Content Preview supports 120+ file types, including most document and image formats, HD video, 3D models, 360-degree images, and 360-degree videos. You can find the full list of supported file types here.

Please note that where supported file types contain references to other objects, for example DWG files, those references are not supported in the Box preview. A notice will be displayed to all end users viewing a DWG file that contains unsupported references letting them know to take alternate steps to complete their workflow.

Demo

Use the navigation arrows to preview different file types.

API

const { Preview } = Box;
const preview = new Preview();

/**
 * Shows a preview.
 *
 * @public
 * @param {string} fileId - File ID to preview
 * @param {string} accessToken - Box API access token
 * @param {Object} [options] - Options
 * @return {void}
 */
preview.show(fileId, accessToken, options);

/**
 * Hides the preview.
 *
 * @return {void}
 */
preview.hide();

/**
 * Prints the current file, if printable.
 *
 * @return {void}
 */
preview.print();

/**
 * Downloads the current file.
 *
 * @return {void}
 */
preview.download();

/**
 * Resizes the current preview, if applicable. This function only needs to
 * be called when preview's viewport has changed while the window has not.
 * If the window is resizing, then preview will automatically resize itself.
 *
 * @return {void}
 */
preview.resize();

/**
 * Adds an event listener to the preview. Listeners should be added
 * before calling show() so no events are missed.
 *
 * @param {string} eventName - Name of the event
 * @param {Function} listener - Callback function
 * @return {void}
 */
preview.addListener();

/**
 * Removes an event listener from the preview.
 *
 * @param {string} eventName - Name of the event
 * @param {Function} listener - Callback function
 * @return {void}
 */
preview.removeListener(eventName, listener);

/**
 * Removes all event listeners from the preview.
 *
 * @return {void}
 */
preview.removeAllListeners();

Parameters

ParameterTypeDescription
fileIdStringBox File ID.
accessTokenStringBox API access token to use. This should have read/write access to the folder above. The value passed in for the token is assumed to never expire while the explorer is visible.
optionsObjectOptional options. See below for details. For example: contentExplorer.show(FOLDER_ID, TOKEN, {canDelete: false}) would be used to hide the delete option.

Options

ParameterTypeDefaultDescription
containerStringdocument.bodyCSS selector of the container in which Preview should be placed
sharedLinkStringShared link URL, required if file is shared and the access token doesn't belong to an owner or collaborator of the file
sharedLinkPasswordStringShared link password, required if shared link has a password
collectionArrayList of file IDs to preview over. When used, this will show previews of multiple files within the same container and expose arrows to navigate between those files. Note that FILE_ID needs to be included in this list and that the SDK doesn't support collections with files that require a shared link or password.
headerStringlightValues that control header visibility and background color. Use none for no header, light for a light header and background, and dark for a dark header and background
logoUrlStringURL of custom logo to show in header. If this value is the string box then the box logo will show
showAnnotationsBooleanfalseWhether annotation button in header and annotations on content are shown
showDownloadBooleanfalseWhether download button is shown in header. Will also control print button visibility in viewers that support print. Note that this option will not override download permissions on the access token.

Token Generator Function

The Preview library optionally takes a token generator function instead of a string token. Using a token generator function allows you to dynamically determine what tokens Preview should use. For example, you can pass in different access tokens for each file or make sure your token is refreshed and valid before showing a preview. The token generator function should return a promise that resolves in either a single string token that applies to all of the files being previewed or a map of typed file IDs to access token for those files.

// Example token generator function that resolves to a single access token
var singleTokenGenerator = function() {
  return someApi.getToken().then(function(data) {
    return data.token;
  });
};

// Example token generator function that resolves to a map of tokens
var mapTokenGenerator = function() {
  return Promise.resolve({
    file_1234: "some_token_abcd",
    file_2345: "some_token_bcde"
  });
};

Events

The preview object exposes addListener and removeListener for binding to events. Event listeners should be bound before show() is called, otherwise events can be missed.

const listener = (value) => {
  // Do something with value
};

// Attach listener before calling show otherwise events can be missed
var preview = new Box.Preview();
preview.addListener(EVENTNAME, listener);

// Show a preview
preview.show(...);

// Remove listener when needed
preview.removeListener(EVENTNAME, listener);

EVENTNAME can be one of the following:

  • viewer event will be triggered when we have the viewer instance first available. This will be the same object that is also a property included in the load event. Preview triggers this event before load so that clients can attach their listeners before the load event is triggered.
  • load event will be triggered on every preview load when show() is called or if inter-preview navigation occurs. The event data will contain:
error: 'message', // Error message if any error occurred while loading
viewer: {...},    // Instance of the current viewer object if no error occurred
metrics: {...},   // Performance metrics
file: {...}       // Box file object with properties defined in file.js
  • navigate event will be triggered when navigation happens. The event includes the file ID of the file being navigated to, and this event will trigger before load.
  • notification event will be triggered when either the preview wrapper or one of the viewers wants to notify something like a warning or non-fatal error. The event data will contain:
message: 'message', // Message to show
type: 'warning'    // 'warning', 'notice', or 'error'
  • viewerevent Each viewer will trigger its own sets of events. For example, the Image viewer will trigger rotate or resize, etc. while other viewers may trigger another set of events. The preview wrapper will also re-emit events at the preview level, with event data containing:
event: EVENTNAME,         // Event name
data: DATA,               // Event data object
viewerName: VIEWERNAME,   // Name of the viewer. See VIEWERNAME above
fileId: fileId            // The file ID

Example event usage

var preview = new Box.Preview();
preview.addListener("viewer", viewer => {
  viewer.addListener("rotate", () => {
    // Do something when a viewer rotates a preview
  });
});

preview.addListener("load", data => {
  const viewer = data.viewer;
  viewer.addListener("rotate", () => {
    // Do something when a viewer rotates a preview
  });
});

preview.addListener("viewerevent", data => {
  if (data.viewerName === "Image") {
    if (data.event === "rotate") {
      // Do something when an image preview is rotated
    }
  } else if (data.viewerName === "Image360") {
    if (data.event === "rotate") {
      // Do something different when a 360-degree image is rotated
    }
  } else {
  }
});

preview.addListener("rotate", data => {
  if (data.viewerName === "Image") {
    // Do something when an image preview is rotated
  } else if (data.viewerName === "Image360") {
    // Do something different when a 360-degree image is rotated
  } else {
  }
});

Scopes

If your application requires the end user to only be able to access a subset of the Content Preview functionality, you can use Downscoping to appropriately downscope the Access Token to a resulting token that has the desired set of permissions, and can thus, be securely passed to the end user client initializing the Content Preview.

Below are a set of UI Element-specific scopes to go alongside Downscoping. These allow developers to enable/disable UI controls on the Content Preview by configuring the appropriate scopes on the downscoped token. To learn more, see Dedicated Scopes for Box UI Elements.

Base Scope

Scope NamePermissions granted
base_previewAllows the user to preview the file, nothing else

Feature Scopes

Scope NamePermissions granted
item_downloadAllows downloading/printing the content from the generated preview
annotation_editAllow user to edit annotations (delete). Note: For highlight annotations to work, the text layer on the document needs to be enabled for the user. Text layer is disabled for all users that don't have download permissions on the file. To enable highlight annotations for a user, please ensure they have download permissions on the file.
annotation_view_allAllows user to view all users' annotations.
annotation_view_selfAllows user to view their own annotations only.

Enable highlight annotations with scopes The highlight scope is not included

with annotation_edit and annotation_view_all scopes. The downscoped access token will need to include the item_download scope to enable highlighting.

Sample Scenarios

ScenarioScopes
User should only be able to preview (not download/print, annotate)base_preview
User should be able to preview, download and printbase_preview + item_download
User should be able to preview and view all annotations (not download, print or create annotations)base_preview + annotation_view_all
User should be able to preview, and create annotations but only view their own.base_preview + annotation_view_self + annotation_edit
User should be able to preview, edit annotations and view all annotationsbase_preview + annotation_view_all + annotation_edit
User should be able to preview and only view their own annotations but not add/delete (ex: after review period has expired, all documents need to be stored in read only mode)base_preview + annotation_view_self