This section outlines the guidelines you must follow when using the CMS tool to submit media files. Please adhere to these guidelines to ensure the content submission process goes smoothly.

The following are media files that can be included in your resource:

Key:  (tick) = supported   (error) = not supported 


Acceptable audio file format:  MP3. 


The following document formats are supported for import:

Supported document formats
Import File TypeSupported

DOC (Microsoft Word) / DOCX

TXT (Text)(tick)
PDF (Adobe's Portable Document Format)(tick)
XLS (Excel File) / XLSX(tick)
OpenDocument (ODT)(tick)

Notes about documents:

  • Because documents need to be downloaded for use, they are not converted and maintain their original format. 
  • If you do not want your document to be editable and you would like it to retain the layout and formatting you've applied, submit it in the print-ready PDF format PDF-A (
  • If your document should be editable, you can:
  • Viewing documents is generally done with Microsoft Open Viewer
    • Documents with the following extensions are viewed using the standard browser behavior: .pdf, .html, .notebook, .htm, .swf, .txt, .do, .pub, .3ds, .epub, .psd. Any other invalid format is included here.
    • After uploading a new document, the user must check that it is correctly displayed in the viewer or uncheck this option in the CMS.
    • Word and PowerPoint documents larger than than 10MB and Excel documents larger than 5MB are opened using standard browser behavior.


File types NOT supported: EPS, AI, TIF, BMP

Acceptable image formats
Type of ImageSupported File Type


Poster ImageJPG
Collection imagesJPG
Support Materials imagesJPG
Type of ImageRequirements
Poster Images (and thumbnails)
  • LearningMedia requires a poster image for all assets. If a poster image is not added to an asset, the poster image from the media file displays.

  • File format: JPG
  • Poster images should be 1920 pixels wide by 1080 pixels high and have a 16:9 aspect ratio.
  • Minimum image size accepted is 700 pixels wide by 394 pixels high.
  • The poster image is resized automatically for lists (thumbnail size) and resource pages (poster image size, i.e. the image you see before you hit the play button).
  • For videos, a representative frame should be chosen, if copyright allows.
  • For documents and audio, use a representative image or icon.
  • See more about poster images
  • Attach your logo to an email and send to
  • We strongly recommend including at least one logo on each resource (typically the Contributor logo).

  • Add logos in the Attributions field at the Content Project level.

  • All logos should be submitted with a minimum width of 250 pixels.

  • File format: PNG (must be transparent)
  • All logos display in color.
  • You can include an unlimited number of Brand, Contributor, Funder, and Producer logos.

  • See more about logos

Image sizes

All sizes are displayed as width x height. 

ImageFile formatMinimum sizePreferred sizeAspect ratioAdditional Notes


(click to enlarge)

Resource Poster ImageJPG700 x 3941920 x 108016:9

LearningMedia requires a poster image for all assets. If a poster image is not added to an asset, the poster image from the media file displays.

For videos, a representative frame should be chosen, if copyright allows.

For documents and audio, we would like to have a representative image, or icon.


Thumbnail on Search ResultsJPG116 x 65 1920 x 1080 16:9

The poster image is resized automatically to create the thumbnail image.

Collection Feature Image

JPG500 x 500500 x 5001:1

Collection BannerJPG1170 x 150  1170 x 150 


Collection ThumbnailJPG600 x 3381920 x 1080 16:9

Support Material Poster ImageJPG450 x 364450 x 364 ---


FLASH IS NOT RECOMMENDED. Schools and institutions do not always run the most cutting-edge version of the Flash Player and .swf files do not work on many tablets.

Pointer assets open in a pop-up of 1045x810 and LTIs open in a pop-up of 1200x756. From the console, click the Open in new tab checkbox to have your asset open in a new browser tab. Learn more

HTML Guidelines

  • HTML may be written according to the HTML 4.01 Transitional, XHTML 1.0, or HTML5 doctype.
  • All HTML files must declare a valid doctype. (HTML will be validated against W3C guidelines. It is suggested that all files are validated before submitting to PBS.  There are free utilities available to achieve this.)
  • HTML must be Section 508 compliant.
  • Interactive developers should follow best practices of web development for HTML, CSS, and JavaScript, including the use of non-blocking JavaScript loads and supporting the widest array of browser technologies possible.

Target browsers

The following is a list of target browsers:

  • Google Chrome
  • Firefox 60+
  • Safari 14+
  • Microsoft Edge

LearningMedia Technical Requirements can be found here:

Interactive Package Construction 

  • Interactives that contain multiple files should be delivered in ZIP archives containing all required files and directory structures needed to experience the object.
  • At the root of the ZIP archive should be a manifest file called manifest.txt. The manifest should contain the following information, and nothing else:
    • Title: Title of interactive
    • Creator: Creator of interactive Creator
    • Email: Email of interactive Creator
    • Description: Short description of interactive
    • Date Created: Date interactive was created
    • The ZIP archive should also contain an index.html file at the root of the archive
  • Only the index.html and the manifest.txt files should be located in the root of the archive. All other files should be contained in a subdirectory called content.
  • Within the content directory, interactive creators may use whatever directory structure they choose, as long the guidelines outlined below are followed:
    • Reference files and directories with the correct letter case.  Filesystems are case sensitive. Capital letters may be used, but it is imperative for developers to realize that they must reference files and directories with the correct letter case. If the HTML, JavaScript, or CSS of your interactive references "filename.jpg" and the actual file is called "fileName.jpg" then your interactive may appear broken to the end user. This would cause your interactive to be rejected by PBS staff. (This is generally only a problem for developers working on case insensitive platforms such as Windows.) To avoid complications with filename references, it is recommended to avoid any uppercase letters in filenames.
    • Do not include spaces or special characters in file or directory names.  No spaces or special characters are allowed in file or directory names. The only special characters that are permitted are: dash ( - ), underscore (_), and period (.). So this-file_name.txt is valid, but this file~name.txt is not valid.
    • All linkage in any interactive should be self-contained and relative to the pathing within the zip archives. For example, the index.html file may embed the object content/css/main.css as a valid path and file. However, /content/css/main.css will not be a valid path or file on the production system.
  • All interactives will be loaded via the index.html file in the root directory. This file should bootstrap the interactive to run for the user.

The structure of the content directory may take on a much wider variety of appearances. Figure 1 demonstrates a sample content directory.

Figure 1





UI/UX Guidelines

Interactives are experienced through different platforms and devices. So in addition to designing the interactive for the appropriate audience, it is helpful to keep in mind some tips to make the interactive accessible for a variety of platforms and interfaces.

(tick) TIPS
Variable display resolutions The interactives may be viewed on a wide variety of displays with varying resolutions so, where possible, use vector graphics. It is recommended that wherever possible, HTML-based interactives utilize a fluid layout in order to make the best use of available display resolution.
Avoid hover events A hover event is any event that occurs upon hovering the mouse cursor over an object on the screen. JavaScript allows for this type of event.  These types of events should be avoided in order to better support touch-based interfaces. If an onHover event does not impact the actual functioning of a interactive, it is allowed. However, if an onHover event prevents users on a touch-based device from experiencing the core functions of a interactive, then those onHover events will require alteration.
Provide user -friendly interfaceAlthough mouse pointers and other interface devices provide a high level of accuracy, it is recommended that interactive developers try not to position linked objects too closely together. Give some room to linked elements of your interactive, and allow hot zones to be as large as possible. This will make the interactive more accessible to differently abled users, will ease interaction with the interactive on touch-based devices, and will expand the audience to a wider age range (younger children tend not to be as precise with the mouse as adults and older children).
HTML links When featuring HTML links as assets, provide the URL that takes the user closest to the media. PBS LearningMedia intentionally tries to avoid cataloging entire websites since we aim to feature discrete resources, so please avoid URLs to home pages, especially if the websites are large.


Videos should not contain web links, hash tags or embedded captions.

360° Videos are also supported but not automatically detected. After uploading this content, the 360° flag must be enabled so the player displays the content correctly.

Standard HD Mezzanine Spec

HD 1080p Mezzanine Spec

File Format

MPEG-4 (.mp4)

*.mov files are acceptable, however, .mp4 is the preferred format.

MPEG-4 (.mp4)

*.mov files are acceptable, however, .mp4 is the preferred format.

Total Stream BitRate5 Mbps  6.5Mbps
Video Stream 


AVC (H.264)  AVC (H.264)  

Frame Size

16/9: 1280 x 720

16/9: 1920 X 1080
Frame Rate30 fps30 fps

Video Standard

Scan TypeProgressive  Progressive  
Video Stream BitRate4808 Kbps  6308 Kbps
Video Stream BitRate ModeVBR  VBR  

Video audio

Mezzanine is the preferred format, however, web delivery is acceptable if mezzanine is not available.

Video files must have audio tracks.

Audio Stream


Web Delivery/COVE Spec


Audio Stream BitRate192 Kbps 48 Kbps

Audio Stream BitRate Mode


Number of Audio Channels

2 (Stereo) 1 (Mono)
Audio Channel's PositionsL, RC
Sampling Rate48 KHz44.1 KHz 
Bit Depth16 bits16 bits 

** Preferred format.

Closed Captioning

  • When you use one of the caption formats that are supported for ingest, your caption file is automatically converted and stored in the CMS as VTT.
  • Caption positioning will be stripped if not supported.
  • Embedded captions are not supported.
Acceptable caption formats
File TypeSupported for ingestSupported for positioning


SAMI  (tick)(error)
QuickTime text(error)(error)

** Preferred format.

When a user hovers their mouse over your video, a variety of icons appear at the bottom of the screen.

  • If the bar contains a CC icon (Figure 1.1), that means your video contains closed captions.
  • If the CC icon does not appear, closed captioning is not available for your video.

When activated, captions display at the bottom of the video.  Learn more about closed captioning

Figure 1

FCC Online Captioning Regulations

Captions are required on all video files (including, but not limited to, those required by law). Captions of online video programming must be at least the same quality as the captions shown on TV. The FCC requires the copyright holder of the content to notify the distributor as to whether captions are necessary for a particular program and to provide the digital captioning file, if necessary. In addition, digital closed captioning is required to be present and accurate for clips, excerpts and segments.

Full text of the online closed captioning regulations can be found here: FCC regulations


Acceptable caption formats
File TypeSupported for ingest

What is ASCII?