Reddit improves accessibility and SEO through Azure Cognitive Service for Vision image and caption generation

Adding captions to expand accessibility and improve SEO

Reddit is a community of communities where people can share and explore content based on their interests, hobbies, and passions. Users can create their own communities, known as subreddits, dedicated to topics that interest them. Registered users, known as redditors, can post content to subreddits including links, text posts, images, and videos, which can be voted up or down by other redditors—either to reward good content or hide low-quality content. 

To improve accessibility for users, including people with impaired vision, Reddit decided to explore how AI and ML tools could help. With millions of existing images on the platform and hundreds of thousands more uploaded each day, the company wanted to find a computer vision service that could quickly produce high-quality captions for use as alternative text (alt text).  

“Our primary goal was to improve image accessibility and discovery,” says Tiffany Ong, Product Manager of Guest Experience and SEO at Reddit. “We believed adding accurate, descriptive alt text to our images would help achieve this.” 

Choosing a computer vision solution

Reddit investigated several AI-based caption generation services, going through a few rounds of testing to analyze caption quality on many types of images, from pictures of animals to landscapes, people, and drawings. The organization chose Microsoft Azure Cognitive Service for Vision to support automatic caption generation. 

“We were impressed by the accuracy and detail of the captions the Microsoft service generated,” says Ong. “Additionally, the API and service are easy to use, images were processed quickly, and Microsoft offered ample support, including great documentation.” 

The Reddit team met with Microsoft regularly during the onboarding process. “Microsoft was very responsive to our questions and made custom adjustments to meet our needs, such as manually increasing our rate limit to accommodate the volume of images we have,” says Ong. “We also appreciate their commitment to responsible AI and are happy with the careful measures taken to ensure the captions are accurate and in compliance.”   

The company plans to use Azure Cognitive Service for Vision to generate captions for millions of images already on the Reddit platform and for all images uploaded by users on an ongoing basis. “With Microsoft Vision technology, we are making it easier for users to discover and understand our content,” says Ong. “The newly created image captions make Reddit more accessible and give redditors more opportunities to explore our images, engage in conversations, and ultimately build connections and community."

Improving accessibility and search success with an easy-to-implement solution

After generating millions of alt text captions using the Microsoft service, Reddit content will be more accessible to users who are blind, have low vision, or are using low-bandwidth internet connections. Alt text plays a key role in making images more accessible for those who use screen readers to understand image content—so for those users, higher caption accuracy means an improved experience. “We were looking for very detailed captions, so users who use screen readers can understand the images more fully,” Ong explains. Reddit wanted a service that could detect both objects and actions within an image, then describe both in written form. “The captions contain an impressive range of vocabulary and have a level of detail that goes a step above mere object detection. Because of this, we found them suitable to use on Reddit. 

Since adding captions as alt text, Reddit has seen a significant increase in SEO traffic to their images. “Adding alt text to our images helps search engines understand them better and makes them more discoverable,” Ong says. “Ultimately, this drives more traffic to our platform.” 

The Microsoft solution also offered advantages from a cost- and time-saving perspective, says Catarina Oliveira, Engineering Manager, Guest Experience & SEO at Reddit. “We were able to build this project without requiring ML engineering support because we used out-of-the-box tools. If we’d built it all ourselves, it would have taken at least twice as long to develop.”

Catarina says Reddit will continue to work with Microsoft technology to generate captions for new images uploaded to the platform. “We’re looking forward to using Azure Cognitive Service to provide best-in-class alt text captions for the millions of images on Reddit’s platform,” says Catarina. “This project enables more people to find and access our content, supporting our goal to extend accessibility to all.” 

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