Dungeons and Dragons (which I'm shortening to D&D from here on in) has been around for decades, ever since Gary Gygax and Dave Arneson published their original box in 1974. Back then, it was all pen to paper - MAYBE you had a handheld calculator to handle the numbers. But it's the Digital Age now, and there are tools out there to make all aspects of D&D easier for players and dungeon masters (DMs) alike. Here are 5 that I've checked out since I started playing.
This website is my saving grace. Its main purpose is tracking content, like your characters, spells, etc. When I made my first character, I walked away a bit confused from the paper-and-pen session, so I plugged all of her details into OrcPub, and it gave me a concise layout and the ability to tweak her to my needs as a newbie. It even generates a beautiful PDF that includes your character sheet, stats, backstory, features, and spell references! Talk about handy.
You can also use OrcPub to create homebrew content. Races, classes, monsters, and items can all be created with a simple online form, and its stored on your browser so you can access it whenever you need it.
The only thing about OrcPub is that they have the rights to publish only a FRACTION of the content that D&D has to offer. If you want something from, say, Xanathar's Guide to Everything, then you have to enter its details yourself. They've launched a petition for whoever holds the rights to D&D content to allow them to publish it: here's a link, if you feel like supporting this fantastic website.
This website has all of the tools that you would need to have a successful campaign, whether it's as a DM or as a player. Just make a free account, and you have access to DM tools like a page that shows all the info you'd have on your DM screen, an Encounter planner, a place to keep notes, and the ability to create a party of other site users and keep track of their stats. You also have tools for players, like a comprehensive character creator where you can track your ability scores, hit points, the damage you take during fights, and your inventory. There's also a chat function for players and DM to communicate through.
The only thing about Adventurer's Codex that I'm finding that it's not super friendly for homebrew content. You'll kind of have to play the original content of the game in order to get the most out of it. But if that's your niche, then Adventurer's Codex is definitely something that will make your campaigns infinitely easier.
Being a baby DM, I haven't looked too closely at this one, but so far, it seems like a great tool for the enthusiastic DM. Natural Crit offers two tools: The Homebrewery, where you can organize your content and style it so that it looks just like the official handbooks (which is pretty cool). This process uses Markdown, which I'm not super familiar with as of yet, but it seems pretty easy to use.
The other tool is the ability to create Achievement Badges for your players, adding another fun layer to the game. These little badges are completely customizable with text, colors, and images. So, if you're looking to award the Best Fighter or the Biggest Klutz, Natural Crit has your back.
This isn't strictly a D&D tool, but it's making creating my homebrew content a dream. This writing tool lets you create all aspects of a world - races, countries, religions, creatures, deities... anything that you could think of to make your content come to life. Not all of the features are free to create (I know, boo!) but the subscriptions are pretty reasonably priced, and you can still do a lot with the features that are free. The layouts are beautiful and navigation is a breeze. I would recommend this for anyone who's creating anything remotely like a D&D campaign - writers, screenwriters, playwrights, game developers, everyone.
This isn't strictly a 'tool' exactly, but I find it's really good for visualizing your characters, even if you don't buy them. Hero Forge is a website where you create a custom miniature (essentially a game piece) of your character. The level of customization on these things is incredible; clothing, expressions, hair, facial features, and physical measurements are all at your fingertips so that you can create the perfect tiny character. You can have them made as plastic or metal figurines, either at the standard size or bigger, if you want to build a shrine to your character or something. There's even an option to put a loop on their head so that you can make your character a necklace, or a cute Christmas ornament. Figures begin at $20 USD, and they add a little more customization to the game, if you're looking for that.