What is this about?
Remember the SV Hatching trick from early XY? It still works in Sun/Moon (it never actually disappeared after Instacheck died; other methods existed)! For those who don't know what TSV and EVs are...

/r/SVExchange
Each trainer has a 4-digit value assigned to them, called a Trainer Shiny Value, or TSV. Every egg also has a 4-digit value called an Egg Shiny Value, or ESV. If the egg is hatched on a game where the ESV and TSV match, it hatches as a shiny Pokémon!

For more info as well as a database of current TSVs:
https://www.reddit.com/r/SVExchange/

Is this method legit?
Now some might ask: This is hacking/cheating, isn't it? Nope, it is not because your save file and Pokemon are not actually being altered by KeySAVe or another third party device/program. You merely are using it to datamine your Battle Video files (which you've copied from your SD card to your computer) to figure out the right person to have hatch the egg. This is significantly faster than using the Masuda Method and Shiny Charm, where not only are the rates still poor, you may not get a 5/6IV mon anyway, and thus would have to possibly Bottle Cap it. It's also better than SOS because those don't even have Egg Moves (and usually only are 4IV max).

Obtaining your ESVs and TSV:
For cart players; they can check their eggs via saved battle videos from the ingame Battle Royal. Battle Royals do not actually make you save the game, which allows you to record a video of the entered Pokemon w/o saving; which in turn lets you get the ESV of unhatched Pokemon by hatching them, entering BR, saving the video, then exiting the game w/o saving the main file. Note regarding PowerSaves: Checking ESVs with PowerSaves does NOT work in Gen 7; don't bother wasting your money on it if you want to check TSVs/ESVs.

However, you do need to do some preliminary steps to get KeySAVe to read your Battle Videos. You first need to break the encryption on your save file's first Battle Video slot (note: this isn't hacking/editing your save file; you're just putting saved battle videos on to your computer, and not back on to the SD card). The guide in question is in the next post. You only need to do this part once per save file.

One small (current) catch...
At this time, the subreddit dedicated to this is current low on TSV entries; with only current about 400+ out of 4096 possible TSVs. The GameFAQs TSV database thread also has not been made yet (the XY and ORAS boards had one), but it should get remade soon (if the managers of said thread read this: don't rush yourselves though!). However, the lack of TSV entries is only due to a lack of awareness; I still hear from people thinking that this method died with Instacheck (far from the truth). This thread however is being made to increase awareness of the fact that the method still works. ATM, you can contribute by adding your own TSV to the Reddit database, or have it written down for when the GameFAQs one is remade. Even with the lack of hatchers though, this is still faster than Masuda/ect.

Checking guide in next post...
3DS FC: 0533-4894-2073 | IGN: Sol
delete
SunSolGold (Topic Creator)4 days ago#2
First, you'll need to download KeySAVe:
https://github.com/Cu3PO42/KeySAVe/releases

Steps to breaking your BV encryption:
1: Delete any Battle Videos you have saved on your SD card from the ingame BV menu.
2: Have two or more Pokemon with you in your ingame party. You might as well make your party full.
3: Find a friend to battle you online (same friend for both battles; please don't ask a random in Plaza).
3.5 (optional): If your friend doesn't know about Battle Royal ESV checking, tell them so that they can break their encryption together along side you by reading these steps if they take interest!
4: Select your ingame party as the group to enter.
5: At the actual team preview screen however, the game will ask you to select which Pokemon to participate. Enter only one Pokemon, then start the battle.
6: Forfeit first thing, then save the battle video to your SD card.
7: Exit S/M, then use either an SD Card reader (Old 3DS) or Micro SD manager (New 3DS). Navigate to this folder on your SD card:
Nintendo 3DS/x/x/extdata/00000000/00001648/0000000 (x being the random letters/numbers; it's different between others).
8: Copy the highest numbered file (the one at the bottom of the list) from your SD card to your PC, and rename the copied file on the computer to -1.
9: Start up S/M, then delete the Battle Video from the ingame menu.
10: Battle your friend again with the same team, but this time, enter any other Pokemon in your party as First, and the Pokemon you entered in the previous battle as Second. Do not enter anything else.
11: Like before, forfeit, save video, copy file to your computer, and rename said file to -2 this time.
12: Go into the Breaking Tab in KeySAVe, and select -1 and -2 as the two files. Remember to change the file type you search from SAV to Battle Video. You should get a encryption key saved, so now it's time to check Battle Royal videos!
13: If your looking for your own TSV (if you don't already know it), open one of -1 or -2 in the Dumping tab. Then go into Options -> Formatting Options -> TSV. Be sure to change it back to ESV after getting your TSV.

Checking Battle Royal videos for an Egg's ESV:
1: Delete any Battle Videos you have.
2: Take up to 3 unhatched eggs you want to have shiny hatched, then hatch them (do not save!)
3: Enter the Battle Royal ingame with the three Pokemon, and lose horribly :P. Note there is a species clause, so if you want to check multiple of the same species, you may have to evolve some of them via a quick level up or use of evolution stones.
4: Save the Battle Video, then close the game w/o saving.
5: Copy the BV on to your computer.
6: Using the Dumping tab, open your Battle Royal Video. You should see the ESVs, IVs, Hidden Power, and the like of your Pokemon!
7: Using the TSV databases, find a player with a TSV matching your egg's ESV, and have them hatch it. It is HIGHLY recommended that you "prehatch" your egg by getting it nearly close to hatching. Getting the egg summary to "It's making sounds, it's about to hatch!" should be enough.
7.5: If you can't find anyone with a matching TSV, you may have to wait for someone with that TSV to pop up in the database, or just to shiny hatch with a different egg. Entering your own TSV (s) will help greatly!