I have most of the 5e books physically. I am looking to use D&D Beyond to build a compendium of spells from various books to be easier to look up, without carrying several books to a session. I see that I am able to just buy the spells from various books. However, they appear to be missing a massive amount of spells. The PHB Spell purchase says there are 57 spells, Xanathar's says there are 52. There's dozens of missing spells if those counts are accurate. Am I missing something here? Any help is appreciated. Google did not answer my question after about 30 minutes. Thanks everyone!

Someone can correct me if I’m wrong. But I believe the PHB only has spells that aren’t SRD on it. Otherwise there would be a bunch of duplicate spells. Spells like Magic Missile and Wish and such won’t show up on the PHB page because you can already access them for free. Something I have noticed though, the spells with the trademarked names and the trademark free names double up. So you’ll have the spells Arcane Hand and Bigby’s Hand. Tiny Hut and Leomund’s Tiny Hut. Magnificent Mansion and Mordenkainen’s Magnificent Mansion. As for Xanathar’s Guide. Some of the spells in the Elemental Evil Player’s Companion were reprinted in Xanathar’s. The Player’s Companion is available for free on D&D Beyond, so that stuff wasn’t put in. 

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I have most of the 5e books physically. I am looking to use D&D Beyond to build a compendium of spells from various books to be easier to look up, without carrying several books to a session. I see that I am able to just buy the spells from various books. However, they appear to be missing a massive amount of spells. The PHB Spell purchase says there are 57 spells, Xanathar's says there are 52. There's dozens of missing spells if those counts are accurate. Am I missing something here? Any help is appreciated. Google did not answer my question after about 30 minutes. Thanks everyone!

 Hi there. Those “missing spells” might be the ones we can access for free as part of the Basic Rules & SRD, as well as the Elemental Evil Players Companion. Since those publications were released for free by the games publisher, WotC, DDB also hosts them for free. Since many of those spells also appear in publications such as the PHB, DDB does not “sell them.”

Here is a full list of the spells from just the Basc Rules & SRD: https://www.dndbeyond.com/spells?filter-class=0&filter-search=&filter-verbal=&filter-somatic=&filter-material=&filter-concentration=&filter-ritual=&filter-sub-class=&filter-source=1

Here is the full list from the EEPC: https://www.dndbeyond.com/spells?filter-class=0&filter-search=&filter-verbal=&filter-somatic=&filter-material=&filter-concentration=&filter-ritual=&filter-sub-class=&filter-source=4

Here is the list from everything else (not including Unearthed Arcana): https://www.dndbeyond.com/spells?filter-class=0&filter-search=&filter-verbal=&filter-somatic=&filter-material=&filter-concentration=&filter-ritual=&filter-sub-class=&filter-source=44&filter-source=21&filter-source=48&filter-source=31&filter-source=6&filter-source=26&filter-source=20&filter-source=52&filter-source=41&filter-source=3&filter-source=54&filter-source=49&filter-source=59&filter-source=62&filter-source=43&filter-source=38&filter-source=7&filter-source=47&filter-source=56&filter-source=55&filter-source=40&filter-source=8&filter-source=5&filter-source=33&filter-source=57&filter-source=60&filter-source=9&filter-source=2&filter-source=10&filter-source=11&filter-source=34&filter-source=53&filter-source=58&filter-source=51&filter-source=12&filter-source=50&filter-source=13&filter-source=42&filter-source=14&filter-source=17&filter-source=18&filter-source=16&filter-source=28&filter-source=25&filter-source=22&filter-source=15&filter-source=35&filter-source=36&filter-source=37&filter-source=19&filter-source=27

I hope this was helpful.

Thanks so much! You both nailed it. That appears to be the issue. Thanks so much for your help!