There's no definitive answer to this question as popularity can change over time, but as of right now, the most popular filter on Instagram is the Clarendon filter. Clarendon is a bright and vibrant filter that's perfect for adding a bit of excitement to your photos. It's also one of the most versatile filters, looking great on a wide range of different types of photos. If you're looking to add a bit of extra pizazz to your Instagram photos, Clarendon is definitely the filter for you!