Adobe XD, is an all-in-one UI design tool, with which you can design beautiful wireframes and interactive prototypes with animation. It works with both Mac and Windows and is for free. They also recently added collaboration.
A fantastic powerful new platform inspired by the world’s best design teams. Design, prototype, and animate—all in one place which works on both Mac and Windows. Do give it a try. They have fantastic support, learning resources, and UI kits.
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Whimsical (only Low Fidelity)
The Balsamiq killer, this blazing fast tool is perfect for people to rapidly visualize their low-fidelity wireframes digitally. It is super intuitive with quick short cuts and pre-made components for almost every use case.
If you're not convinced we recommend viewing their Zappos, Shopify and Dropbox example projects to get a better understanding of it's capabilities.
Framer, is the most powerful interactive prototyping tool out there where prototypes are built using code. This means it comes with a steep learning curve and many a times takes more time than necessary to make simple interactions. A great tool but we recommended using it to create only extremely complicated interactions.
Lingo is the visual home for your brand. Stop wasting time looking for files buried in folders. Visually organize all your assets in one place with Lingo. Create and share living style guides, asset libraries and more.
A fantastic free tool which analyses your website's accessibility against the Web Content and Accessibility Guidelines. It provides you with fantastic detailed documentation on how you can fix each issue on your website. Do check it out.