Spell Access

The spells of the Player’s Handbook and other Core Rulebooks (such as Sword Coast, Xanathar's, and Elemental Evil, not UA) are considered the “known” spells of the world, spells from the Player's Handbook are commonly disseminated and practiced, while the other spells are less well-known, but still passed on. But these are not the only spells available.
To Know, Prepare, Pray for, etc. a spell not in a Core Rulebook, a character must learn of the spell somehow. Maybe a cleric or druid has seen another cleric cast that spell, or been given secret knowledge from a temple or circle. The paladin’s mentor has shown his squire a new smite he has learned. An ancient spirit has revealed a new secret to the questing druid of ranger. A sorcerer, warlock or wizard discover an ancient spellbook with spells that had been lost to time (or newly researched).
Even new Cantrips need to be found. While many wizards don’t include their cantrips in their spellbooks, a wizard who has researched a new cantrip would likely include it in his spellbook in order to share it with others. The library of the mage’s guild likely has all sorts of cantrips in its collection, to teach new mages and to preserve for posterity.
Once discovered, each spellcasting class interacts with the spell in different ways. The Cleric, Paladin, and Druid can pray for the newly found spell in addition to any spells in the PHB, the Bard, Ranger, Sorcerer, and Warlock may add the spell to their “Spells Known” when a new spot opens up (or they can switch it out with a known spell per the rules of their class). The Wizard may add the spell to their spellbook, or learn the new cantrip when a new cantrip slot opens up.
Any new spells introduced into the game will be added to this website, under the Spells and Magic tab, once they are found by the players.