Jelly.Tools is free to use and always will be. Ads help cover hosting costs — if you'd like an ad-free experience and to directly support development, you can become a Patron.
£3/month gets you ad-free access. Higher tiers are available on Patreon too if you'd like to support the project more, but grant the same ad-free access for now — some tiers may unlock extra perks in the future.