What is the Community Digital Library?

The Community Digital Library (CDL) is an online and open-source collaborative knowledge management platform. You can take markdown-style notes, connect them together, visualize them, share them across communities, and search or discover submitted and indexed content related to your interests. We offer a website and a Chrome extension, all for free.

The CDL provides various features and functionalities to enhance your online learning experience. On this page, we outline everything you need to know about CDL, and how to best use the CDLto achieve your goals.

Background and Motivation

The CDL project began in the fall of 2022, and its original purpose was to support an information retrieval and ranking course assignment at the University of Illinois Urbana-Champaign. The original development was done by Kevin Ros, the TA at the time, who created a basic version of the CDL to be used in the course. As the semester progressed, Kevin and his PhD advisor/course instructor, Dr. ChengXiang Zhai, realized that the CDL could be generalized to a much more powerful online platform that could support numerous features, act as a sandbox for researching retrieval and recommendation, and allow the collection of various data sets to study user interactions. Since the fall of 2022, Kevin had led a team of developers, from the University of Illinois, under the supervision of Dr. Zhai, to build the CDL into what you see here today. And the CDL has become a central component in Kevin's PhD thesis.


The purpose of the CDL depends on you and your goals:

  • As a user, the CDL offers numerous features to help save, organize, and discover online information. We provide more information in the following sections outlining these features and how best to use them.
  • As a developer, the CDL is open-source, and we encourage you to suggest or implement any feature that you think would be helpful for your experience while using the CDL. If you aren't sure where to begin, then reach out to Kevin Ros at [email protected].
  • As a researcher, the CDL can be used to perform studies on user interactions over webpages, searches, ranking formula, and recommendation. And due to the CDL being open-source and runnable fully locally, you have the flexibility to modify the CDL to fit your study's needs.


The CDL has been built on and has led to numerous publications and posters:

Our current and future research projects include many exciting directions, including contextual search, automatic content organization, content visualization, chatbot integration, and user studies. We are always looking for collaborators; if you would like to get involved, then please reach out to Kevin Ros at [email protected].


Creating an Account

You must make an account before you can begin using the CDL. An account can be created here. Note that accounts made on the website will not work when running the the service locally through localhost, so you will need to create separate accounts.

Installing the Extension

The Chrome extension is available in the Chrome web store and can be installed from here. After installing, you will be able to log into your CDL account that you created using the CDL website. The extension defaults to logging in users via the hosted version of the CDL, so if you wish to use the extension with your local CDL instance, then you will need to change the extension "Backend Source" setting.


Community Overview

Much like a group chat, a subreddit, or a folder, a community is a way for you and your peers to logically organize content on the CDL. You can create, join, or leave communities, and any member of a community can search for or browse all content present in the community. A community can have any number of members, ranging from just yourself (e.g., a private community to save your personal notes) to hundreds of members (e.g., a large class all taking notes together on lectures and textbooks).

Creating a Community

You can create a community by selecting the "Communities" tab in the navigation header bar at the top of the CDL website, and then clicking the "+" in the "Create" box. You will need to provide a name, which should describe the purpose of the community (e.g., "Papers", "CS410 Fall 2023", or "Cool News Articles"). After creating a community, your page should refresh and you should see the newly-created community's card on your screen. If you would like to change the name or add a description, you can click the pen "edit" button on the card and edit the desired details.

Inviting, Joining, and Leaving Communities

To invite another CDL user to one of your communities, you can click the "key" icon of the community's card. Clicking this will copy a join key, which you can then send to another CDL user.

To join a community, you can click the join card's arrow and paste the respective community's join key. Then after clicking "join", your communities page should refresh and you should see your newly-joined community's card.

To leave a community, you can click the exit button on a community's card. In the case that you'd like to rejoin the community, you can either re-enter the join key or navigate to the "History" tab on the Communities page and select the respective community's rejoin button.


The CDL supports the basic visualization of any community's content. To view a community's visualization, you can click the "Visualize Community" on the community's card. This will bring you to an interactive graph where the community's submissions are organized around hashtags, topics, and meta-descriptors.


Submission Overview

A submission is the fundamental building block of the CDL. Submissions are user-created, and consist of an optional source URL, a title, and a description. Submissions can be added to or removed from communities, and if you are are a member of a community, then you can search over, browse, and view all submissions currently added to a community.

The source URL of a submission is to provide you with a way to link external content (e.g., a video, a news article, a published paper, etc.). This field is optional, and if not included, the field will default to the submission's webpage on the CDL website. The title of a submission is meant to give you and other users a brief overview of the submission. And the description is meant to provide you with the ability to create markdown-style notes for whatever you're submitting.

Creating a Submission

You can create a submission by using either Chrome extension's "Submit" tab or by clicking the "+" on the CDL website header. The source URL is optional when using the CDL website header, but while using the Chrome extension, it will be the page that you open the extension on. After adding a title, a description, and selecting a community, you can click "Submit" to save the submission to the selected community.

To check your submission(s), you can click the "Submissions" tab in the header at the top of the CDL website. This will bring you to a page that displays, in reverse chronological order, all of your submissions that you have made to all of your communities.

If you included a source URL and the webpage is publicly available, then the CDL's server will also try to index the webpage. This is why you may sometimes see search results and recommendations with the community listed as "Webpage".

While typing the description, the CDL provides a quick way to connect notes together. By typing "[[search terms]]" followed by a space, the CDL will suggest submissions in your communities related to these search terms. Then, clicking any one of these suggestions will replace the brackets with a hyperlink to that submission. For example, typing "[[cdl demos]] " will return suggestions related to "cdl demos".

Submission Card and Features

The submission card provides you with numerous ways to view and interact with the submission. Clicking the hyperlinked title at the top of the submission card will open the submitted URL in another tab. If no source URL was included, then this will take you to the CDL's submission page. Below the hyperlinked title is the shortened submitted URL and submission time. Below this is the submission's description. And at the bottom left of the submission are the names of the communities that the submission is a part of, and the list of hashtags (if any). Hashtags are automatically extracted from the title and description, and are meant to provide you with a way to easily search for and filter submissions. More information about hashtags can be found in the Search section below. Following searches or recommendations, each submission card will contain relevance judgment buttons at the bottom left. These buttons are meant to provide you with a way to rate the submissions with respect to your query or recommendation context.

Each submission card also contains three dots at the top right corner. Clicking these three dots will open a small menu with multiple options. Clicking the first option, "View Submission", will bring you to the CDL's submission page. On this page, you will be able to view the submission's full title and description, see the submissions views/clicks/shares, add or remove the submission from a community, and edit or delete the submission (if you are the submission's creator). The submission page also displays a basic visualization of the submission with respect to other submissions and webpages. Clicking the "Feedback" button will open a small pop-up window where you can send feedback about the submission to the CDL (e.g., if the submission is inappropriate or the link is broken). And clicking the "Share URL" will copy the URL of the page to your clipboard. This "Feedback" and "Share URL" functionality is also available as the second and third option in the three dot menu. Finally, clicking "Get Connection ID" will copy the submission CDL ID to your clipboard, which is used to reply (described below)

The CDL's submission page also supports the ability to reply to the submission. To reply, you have two options: you can connect an existing submission or create a new submission. To connect an existing submission, you only need to post the submission's connection ID in the field and click submit. And to create a new submission, you need to fill out the information in the presented form after clicking "Reply". In either case, the connected/created submission will be displayed on the source submission's page below its description.


Notes Overview

The Community Digital Library supports a basic, hierarchical, markdown-style private notes. To access your note pages, you can click the "Notes" button in the header at the top of the CDL website. Clicking this will redirect you to a page where you can view, create, edit, and delete your notes.

It is recommended that you instead take notes via submissions through the description's markdown capabilities. This way, your notes can be shared with others, are searchable, and can appear in recommendations.

Creating, Editing, and Deleting Notes

A note page can be created as a top-level page via the "+" next to "Notes" or by the "Create" button (after entering a page name). Once a top level page is created, you will be able to create child pages (up to three levels). Created note pages will appear as a tree on the left-hand side of the screen.

Clicking a note page title will open up the note page on the right-hand side of the screen. Then, clicking the pen icon at the top of the page will allow you to edit the note page title and content. During the process of editing the note, the preview of the rendered note page will be presented on the right-hand side of the editor. To save the note page, you can click the blue save icon. And to the delete the note page, you can click the red trash icon.

Real-time Recommendations

As you are editing your notes, the CDL will provide real-time submissions from your communities that are related to the portion of the notes that you are currently editing. These recommendations will appear below your note page editor, and will be refreshed every 30 seconds given that there are changes to the note.


Search Overview

Searching within the Community Digital Library is a straightforward process. Whether you are looking for specific content or exploring new resources, our search functionality can assist you in finding what you need. You are able to search over all submissions that have been added to your communities, and you can perform searches using either the CDL website or the Chrome extension.

Searching via the Website

To search submissions via the CDL website, you can leverage the search bar in the website header. In this search bar, you can enter keyword-based queries (e.g., "bm25") or natural language questions (e.g., "what is the intuition behind bm25?"). Moreover, you can add hashtags to your query (e.g., "bm25 #Lecture1") to restrict your results to those that match the hashtag. And you can filter searches by community using the dropdown menu to the right of the search bar. By default, the search occurs over all of your joined communities. Following the search, you should see a ranked list of submissions corresponding to your query. You also have the ability to judge the relevance of each result via the submission judgment buttons, thus helping us improve the ranking formula.

Searching via the Chrome Extension

You can perform searches via the Chrome extension underneath the Chrome extension's "Search" tab. The extension supports the exact same search functionality as the CDL website described above. However, opening the "Search" tab will automatically present recommendations according to your current context (e.g., your current webpage and highlighted text, if any). More information about this feature is presented in the Recommendations section below.


Recommendation Overview

The Community Digital Library provides various ways to help you discover submissions made to your communities. The overarching goal of recommendations on the CDL is to provide you with submissions according to your context: your current webpage, previously-clicked submissions, previously-submitted webpages, other members of your community, etc.

Front Page Recommendations

The homepage of the CDL, accessible by clicking the CDL logo at the top left of the webpage header, provides you with two methods of general recommendations: "Explore" and "Most Recent". You can select one or the other via the dropdown menu towards the top of the homepage. The "Explore" method recommends submissions most similar to your most recent submissions. And the "Most Recent" method displays all submissions made to all of your communities in reverse chronological order.

Extension Recommendations

The Chrome extension provides contextual recommendations to you when you open the "Search" tab of the extension. Here, the extension pulls the current webpage's URL, webpage title, and webpage description and uses this to find submissions related to the webpage. The submissions will automatically appear beneath the search bar.

Additional Features and Functionality

Core Community Content

Certain communities often have what we call core content - content that members of a community tend to visit very frequently. For example, a community that was created for a university course could consider all of the lecture videos as core content. The CDL provides various features to help community members organize and discover submissions around this core content.

Any member of a community can make a core submission to a community, which indicates that the submitted webpage is a part of that community's core content. To do so, you should include the hashtag "#core" in either the title or the description of the submission.

Including this "#core" hashtag allows all members of a community to explicitly connect submissions to the core content. For example, suppose the core submission included the hashtags "#core #lecture1", indicating that the submission linked to the first lecture of an online course. Then, any future submission to the community that includes "#lecture1" will be connected to the core submission containing "lecture1". These connections can be seen on the core submission's webpage - when the extension is opened, the automatic recommendations will first present the linked submissions (if any).

The Local Version

If you would prefer to use the CDL locally (e.g., run the server and databases on your computer), then you can follow the directions listed on GitHub. The extension is also locally compatible by changing the Backend Source under the settings icon tab.

Use Cases

Personal Bookmarking

One of the primary use cases of the CDL is personal bookmarking and archiving. This is best supported by creating a community (or communities) according to the type of content that you would like to save. For example, a community where you save interesting news articles could be called "News Articles", or a community where you save academic publications could be called "Papers and Demos". And, as you submit webpages to your personal community, you can add hashtags according to whatever taxonomy you would like to have (e.g., "#empirical" or "#politics"). And after creating the community, you will be its only member, meaning that all bookmarks saved by you are accessible and viewable by only you.

Collaborative Note-taking

Any meeting note, lecture note, or thought can be made into a submission and added to any of your communities. You can collaborate with any sized group - from just yourself in a private community for personal thoughts to a class-wide community taking notes on lecture content. With replies, hyperlinks, searches, and recommendations, you will be able to easily organize and discover notes and external webpages related to your interests and goals.

Lecture Content Expansion

The CDL can also be used for adding and organizing online content relating to course lectures. One pain point of courses prevalent today, especially in online courses, is that students often seek course-related online information independently. For example, while watching a lecture, a student may have a question about something mentioned in the lecture. Then, the student may turn to an online search engine to find webpages helpful for resolving their information need. This is done independently of other students or the instructor. As a result, neither other students nor the instructor can benefit from the student's work of finding helpful course-related information. The CDL aims to mitigate this problem by providing a way to organize online content with respect to the course content and a way to search and discover the online content when in specific course-related contexts.

Instructors who wish to leverage this functionality in their course should first create a course community named accordingly (e.g., "Spring 2023 CS101"). Then, to optionally leverage the core community content feature, they can add each lecture webpage to define a coupling between webpage URL and hashtag. Each submission for the core community content should contain at least two hashtags: "#core" and the hashtag(s) that define this web resource (e.g., "#lecture1", "quiz1", etc.). Once the community is created and the core content is added, the instructor should have each student create a CDL account and send the community join key to all of the students.

Once the students are in the community and begin to consume the core community content (i.e., the course content), they can begin making submissions. For example, suppose a student watches the first lecture ("#lecture1"), and finds that they needed to seek out an additional web resource to understand the concepts mentioned in the lecture. They can then create a submission of that web resource to the course community with the hashtag "#lecture1", and a title/description explaining why the webpage is helpful. Then, the next time that a student opens the Chrome extension on the first lecture's web page, the extension should provide the student's submission as a recommendation.

Over time, as the community content grows, it can be difficult to understand the breadth of the submitted content. The CDL provides a simple visualization of all community submissions with respect to the hashtags. To see this, you can navigate to the Communities tab in the header of the CDL website, and for any community's card, you can click the Visualization icon. This will bring you to a top-down view of the community's submitted content with respect to the hashtags, organized by topics.



The source code for the CDL is available on GitHub. If you notice a bug or would like to add a feature, then we welcome pull requests. If you have an idea for a larger feature or structural change, then please reach out to Kevin Ros at [email protected].


We are always looking for collaborators across research disciplines. Whether it be information retrieval, recommendation, user studies, HCI, or any other area, please reach out to Kevin Ros at [email protected].

The Community Digital Library (CDL) is an online and open-source social bookmarking platform that allows you to collaboratively describe and save, search for, and discover webpages related to your interests. We offer a stand-alone website and a Chrome extension, all for free.



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