How to Build a Reddit Clone with Bubble

What Reddit Actually Does

Reddit is a link aggregation and discussion platform organised into communities called subreddits. Users submit posts (links, text, images, or videos), and the community votes them up or down. The voting system determines what content rises to the top. Comments are threaded, meaning replies nest under parent comments to create branching conversations. Moderators manage each subreddit with tools for removing content, banning users, and setting community rules.

The platform works because of its sorting algorithms. Hot, new, top, and controversial sorts give users different ways to surface content. Karma, the cumulative score from upvotes and downvotes, serves as a reputation system. Reddit is fundamentally a community management platform with content discovery built on collective curation.

Core Features to Build

Your MVP needs communities (subreddits) with names, descriptions, rules, and member counts. Posts within communities supporting text, links, and images. An upvote and downvote system with score calculation. Threaded comments with their own voting. User profiles with karma scores and post history. Sorting options for hot, new, and top posts. Basic moderation tools for community creators including post removal and user banning.

A home feed that aggregates posts from communities the user has joined is essential. Search across communities, posts, and comments rounds out the discovery layer. Flairs, which are labels on posts and users within a community, help with content categorisation and filtering.

Data Types in Bubble

The core data types are User, Community, Post, Comment, Vote, Membership, Flair, and ModAction. User extends Bubble's built-in user with display name, avatar, bio, cake day (join date), post karma, comment karma, and a list of joined communities. Store karma as separate number fields for post and comment karma to avoid recalculating from scratch each time.

Community has name, display name, description, rules (list of texts), banner image, icon, creator (User reference), member count, created date, and settings like post types allowed and who can post. Post belongs to a Community and a User with fields for title, body (rich text), link URL, image, post type (text, link, image), score, upvote count, downvote count, comment count, flair, created date, is pinned, and is locked.

Comment belongs to a Post and a User with body text, score, upvote count, downvote count, parent comment (self-reference for threading), depth level (number for indentation), and created date. Vote is a join between User and either Post or Comment with a value field of 1 (upvote) or -1 (downvote). Use separate Vote types for posts and comments, or a single type with optional references to both. Membership links a User to a Community with a role field (member, moderator, admin).

Flair belongs to a Community with a name and colour. ModAction logs moderation activities with fields for moderator, target user, target post or comment, action type (remove, ban, pin, lock), reason, and timestamp.

Voting System Architecture

The voting system is Reddit's backbone and needs to be performant. When a user votes on a post, first search for an existing Vote by that user on that post. If no vote exists, create a new Vote with value 1 or -1 and update the post's score, upvote count, or downvote count accordingly. If a vote exists with the same value, delete it (un-vote) and reverse the score change. If a vote exists with the opposite value, update it and adjust the score by 2 (reversing the old vote and applying the new one).

Update the post author's karma in the same workflow. This means every vote triggers updates to three things: the Vote entry, the Post's score fields, and the author User's karma field. Run the karma update as a backend workflow to keep the front-end action fast. The same logic applies to comment votes but updates comment karma instead.

For the front end, use custom states to track the current user's vote status on each post in the repeating group. Set the state when the repeating group loads by checking if a Vote exists. This prevents a separate database query for each post when rendering the vote arrows and avoids visible loading delays.

Threaded Comments Implementation

Threaded comments are the most architecturally complex part of a Reddit clone. Each comment has a parent comment field (empty for top-level comments) and a depth field. When displaying comments, you have two options in Bubble. The first is a nested repeating group approach where each comment cell contains another repeating group for its replies. This works but gets slow beyond 3 levels of nesting because each level triggers a new database search.

The better approach is a flat repeating group with indentation based on the depth field. Load all comments for a post in a single search sorted by creation date or score, then use left margin or padding calculated from the depth field to visually nest them. This keeps the search count to one regardless of how deep the threading goes. Add a collapse and expand toggle using custom states to hide replies below a certain comment.

When a user replies to a comment, create a new Comment with the parent comment set to the one being replied to and the depth set to the parent's depth plus one. Increment the post's comment count.

Sorting and Feed Algorithms

Reddit's sort options determine what users see. New sort is simple: order by created date descending. Top sort orders by score descending within a time window (today, this week, this month, this year, all time). Use Bubble's date range constraints on the search to implement the time filters.

Hot sort is the interesting one. Reddit's hot ranking algorithm considers both score and age, favouring recent posts with high scores over older posts with higher absolute scores. In Bubble, you can approximate this by creating a hot score field on Post that gets recalculated periodically. Use a recursive backend workflow that runs every 15 to 30 minutes, searching for recent posts and updating their hot score based on a formula that divides score by hours since posting raised to a power. Sort the feed by this pre-calculated hot score field.

The home feed searches for Posts where the community is in the current user's joined communities list. Apply the selected sort on top of that constraint.

UI Components and Layout

The home feed uses a single-column card layout. Each post card shows the vote arrows with current score, post title, thumbnail (for link and image posts), community name, author, time ago, comment count, and share button. The vote arrows change colour based on the current user's vote status using conditionals tied to the custom state.

The community page has a header with banner, icon, name, description, member count, and join button. Below that is the post list with sorting tabs (hot, new, top) and optional flair filters. A sidebar shows community rules, moderators, and related communities.

The post detail page shows the full post content at the top with vote arrows, then the comment input, then the threaded comment list. Each comment shows the author, time ago, score, vote arrows, reply button, and collapse toggle. The reply input appears inline below a comment when the reply button is clicked, using conditional visibility on a group within the comment cell.

Privacy Rules and Permissions

Public communities make all posts and comments visible to everyone. Private communities restrict visibility to members only. Set privacy rules on Post and Comment to check if the parent Community's visibility setting is public or if the current user is a member. Votes are private to the voter but the aggregate score is public. User profiles show post and comment history publicly unless the user sets their profile to private.

Moderation permissions check the Membership type. Only users with moderator or admin roles in a community can access mod tools like post removal, user banning, and flair management. Use privacy rules on ModAction to restrict visibility to community moderators.

What to Skip in V1

Skip awards and premium features, real-time chat, wiki pages, polls, video hosting, crossposting, multi-community feeds (multireddits), and the recommendation engine. These are all growth features that do not validate whether your community concept works. Build the post, vote, comment loop first. If users are engaging and creating content, you have something worth expanding.

Cost and Timeline

A Reddit clone with communities, posts, voting, threaded comments, and basic moderation takes 6 to 8 weeks for an experienced Bubble developer. The threading and voting logic are more complex than typical Bubble apps, so factor in extra time for testing. Bubble's Growth plan at $119 per month is the minimum for the workflow volume voting generates. Budget $500 to $700 for the first quarter including subscription and plugins. Hiring a developer costs $7,000 to $18,000 depending on scope.

DIY vs Hiring a Bubble Developer

Reddit clones are among the more complex Bubble builds because of threaded comments, the voting system, and sort algorithms. If you are new to Bubble, expect the threaded comments alone to take a week of trial and error. The voting system's three-way toggle (upvote, downvote, un-vote) with cascading updates to scores and karma is another area where incorrect implementation leads to data inconsistencies that are painful to debug.

An experienced Bubble developer will architect the voting and threading patterns correctly from day one, saving you weeks of refactoring. They will also set up the hot sort calculation and backend workflows for karma updates efficiently. If your community concept depends on a smooth Reddit-like experience, investing in professional development pays off.

Ready to Build?

Related guides:

• Bubble discord integration guide

• Bubble auth0 integration guide

Building a community platform that nails the Reddit experience takes architecture expertise. Talk to Goodspeed Studio and get your community platform scoped and built by experienced Bubble developers.