Hello, I'm a fairly new DM to dnd. I got a group of newbies together to play a game and I had the Wizard ask a question about spell creation. Prior to this I had told him it's possible for him to lose all his spells if he didn't have a back up spellbook. So he asked if there was a spell that he could use to "backup his spells to another spellbook automatically". He's a cybersecurity analyst so I should have known. Anyway, I was thinking about letting him create a spell at around 5th level that would give him the chance to "automatically" back up his known spells so far. With a chance at failure of course pending some kind of die roll maybe. Does this sound like a balance spell mechanic?

Check if he wants to be an Order of Scribes wizard. They have a feature that lets them replace their spellbook if lost or destroyed.

School of Conjuration wizards can use minor conjuration to create a temporary copy of their lost spellbook they can then copy / memorise spells from.

If you have keen mind feat and the paper and ink/etc, you can use Fabricate to recreate it from memory in a fraction of the time.

So given the ease of replacing it/securing it, I'd more likely consider it a 3rd level spell at highest - with the components of paper and ink (at cost) being required. I would have the spell similar to Awakened mind, however, to avoid the wizard mass-producing their books instantly. Only one at a time for a spell, anything more - buy a spell book, get the inks and use some downtime.

It's worth remembering this bit from the PHB:

Replacing the Book.

You can copy a spell from your own spellbook into another book. for example, if You want to make a backup copy of your spellbook. This is just like copying a new spell into your spellbook, but faster and easier, since you understand your own notation and already know how to cast the spell. You need spend only 1 hour and 10 gp for each levei of the copied spell.
If you lose your spellbook, you can use the same procedure to transcribe the spells that you have prepared into a new spellbook. Filling out the remainder of your spellbook requires you to find new spells to do so, as normal. For this reason, many wizards keep backup spellbooks in a safe place.

So based on that a spell that can completely replicate your spell book should probably be a no-no.

Having said that there is a way you could do it though using your DM powers and existing mechanics and that would be to have him sign a pact or otherwise come to some arrangment with an Otherworldly patron in a fashion similar to a Warlock taking the pact of tome and being able to get a replacement book of shadows by doing a  hour long ritual, in essence the patron creates the back up spell book and just sends it out when the wizard requests it.

This would not mean he had to sell his soul to get the benefit (but might mean taking a 1 level dip in Warlock to represent the pact at your discretion). This could just reflect that a particularly scholarly patron might agree to provide a copy of his spell book in exchange for some minor service every now and then. This service might be that the patron is actually just collecting spells so whenever the wizard scribes a spell the patron automatically learns it as well or maybe the patron is is using the wizard to unlock some magical secret for them or potentially using them to unlock a magical demiplane where the patron is being held prisoner.

This also means as a DM you can weave whatever macguffins you want into you campaign under the guise of the patron needing the wizard to do something or go somewhere.

I’ve mostly played in Faerun and it (at least) has a long lore tradition of mages creating and secreting spellbooks and magic items in hidden locations as backup supplies for mages who lose everything or die and come back as clones. Manshoon had enough such stashes to outfit at least 12 clones during his clone wars. Elminster always seemed to have a stash or three he can pull from so maybe what he needs to do is create a couple of back ups and stash them where he could get them if needed. The other thing is crafting scrolls - typically my mages are fairly combat heavy with what they have memorized with emergency spells like feather fall as the utility backups prepared. Then they carry around a bunch of acquired/created scrolls for “special occasions” . If you keep the treasure finds balanced with the down time costs for living and scribing you should be good. You might also remind him that his “backup” utility spell would only back up what he has in memory (prepared) anyway and he already has that. If he really wants to create a new spell then yes L5 sounds about right - either for a spell that copies a spellbook/spell into another document (call the spell Xerox 🤪)  with the components being the paper and special inks needed at the standard cost for all the spells being copied.( which ain’t gonna be cheap) but he has to have the spellbook to copy it.  What he is really asking for is a “cloud backup program” spell and that should probably be L8/9 ie only available to archmages typically as they transition from PC to retirement/NPC.

If a wizard loses his spellbook, he doesn't completely lose his known spells, but he can't prepare different spells and is limited to his current preparations until he gets a new spellbook. He can scribe spells he already knows into a backup/replacement spellbook at a reduced cost and time investment, only 10 gp and 1 hour per level of a given spell rather than 50 gp and 2 hours per level. (Order of scribes wizards can replace a lost of destroyed spellbook over the course of a short rest at no cost, but in order to create a second spellbook they still need to spend the time and money to scribe the spells into a separate book.)

Exactly what temery said. Losing your spellbook just blocks you to prepare new spells, which is a barely inconvenience to seasoned Wizards. I think you can even cast rituals without your spellbook, but better double check.

Yep, you can still cast rituals without the spellbook.

Here is what the PHB says:

Ritual Casting

You can cast a wizard spell as a ritual if that spell has the ritual tag and you have the spell in your spellbook. You don’t need to have the spell prepared.

what it doesn’t say is whether this would still hold true if you didn’t have your spellbook available as you caste the ritual. Personally I dont allow rituals by wizards if they don’t have their spellbook available during the casting..

Quote from Wi1dBi11 >>

Here is what the PHB says:

Ritual Casting

You can cast a wizard spell as a ritual if that spell has the ritual tag and you have the spell in your spellbook. You don’t need to have the spell prepared.

what it doesn’t say is whether this would still hold true if you didn’t have your spellbook available as you cast the ritual. Personally I dont allow rituals by wizards if they don’t have their spellbook available during the casting..

 The wizards possess a high INT to remind and store on its own BRAIN the spells, right ?? So taking this ability as is, if you previously have casted the Ritual spell, your brain possess the enough Inteligence to remember it, so the next time you have to cast it, you only need an swift effort to seek&find in your thoughts the enough info to do it. Huh ??? Am I right or the Wizard needs an specific high Int ??

I saw the Wizards can have 1 spellbook for the normal spells, and another 1 for the Ritual spells, as is described in the [Utility]Ritual Caster[/Utility] Feat.

You will notice that even priests that repeat the mass every day use a book to help them make sure they are doing everything correctly.. no matter what the intelligence trying to do a 10 minute + ritual strictly from memory days and weeks after losing a spellbook would make even someone with an idetic memory have problems. At one point years ago (HS days) I managed to quote most of a page of my then favorite scene from Wrinkle in time in an English class 6 weeks after losing the book and how much of that was actually close paraphrasing I’m not sure but that was the most I could do. For spell casting close paraphrasing doesn’t cut it and super high intel does =idetic memory.

The only spells a Wizard actually has stored in his brain (memorized) are their cantrips and their prepared (memorized) spells. So if they prepared a spell that has the ritual tag then yes they could cast it as a ritual, but if it’s taking up a prepared space that is a combat/ utility spell you can’t take. The key point is that a Wizard WITH their spellbook can caste the ritual spells without memorizing them by working out of the spellbook instead. Clerics and Druids have to have prepared the spell to cast it as a ritual without using a spell slot and pretty much all other casters have to take the ritual caster feat to be able to cast rituals at all and then they cast them as the Wizard does out of their rituals spellbook.

There's nothing in the rules that specifies that wizards need to have their spellbook in order to cast rituals or that they can't cast rituals without their spellbook, so therefore they don't need the spellbook in order to cast rituals.

Y'all can argue about the logic of it all you want, and you can house rule all you want that they need the spellbook to cast rituals, but strictly speaking by RAW there's no specific requirement of having it.

Your quite right that there is nothing either way in RAW and you are free to rule as you like if you are the DM. BUT, don’t be surprised when, as the player, the DM rules that RAI you need to be in possession of your spellbook in order to use it to cast rituals.

If you want something more authoritative feel free to send it in to sage advice for a Crawford ruling.