You can manage & track your card collection and decks once you create an account and login.

Term: Sideboarding Rulings
Is it legal to have a copy of Swap Parts in my Side Board that I never put into my actual deck?

No, it is not legal. It is so not legal in fact, that it is illegal.
Source: Wizards of the Coast (2019-06-28)    【Link to Ruling】
Tags: Sideboarding
If I open a card in a Limited Format that says "grab a card from outside the game" am I allowed to dip into my personal collection for this (assuming I brought it ahead of time) or just the sideboard of my Limited Pool? If I have a lesser collection (or am just lazy), am I allowed to use cards from my Sideboard for my Outside-of-the-Game-Board? Or is this a Head Judge for an event decision?

For casual play, you are allowed to use whatever parameters your play group has decided on. For competitive play, in Limited, you are only allowed to draw "outside the game" cards from your Limited pool.

Editor's Note: In our initial ruling, we misstated our answer and accidentally ruled that "outside the game" cards must be limited to one's sideboard. This is incorrect.They later changed competitive rules to require battle cards to come from the sideboard.
Source: Wizards of the Coast (2019-07-12)    【Link to Ruling】
Tags: Sideboarding
What can be in your sideboard?

Sideboards can contain 1 character card of 20 stars or fewer and up to 10 battle cards.
• No more than 3 copies of each Battle Card are allowed between a player's deck and sideboard.
• Duplicate character cards are not allowed between players' decks and sideboards.
• After sideboarding, decks must be legal.
Source: Wizards of the Coast (2019-11-21)    【Link to Ruling】
Tags: Sideboarding
How do you sideboard?

After each game in a match, the player who won that game chooses to sideboard a character
first, and declares their team. Then, the player who lost the previous game does the same. Then
both players swap battle cards between their main deck and sideboard simultaneously.
Players are not required to reveal how many battle cards they have swapped from their main
deck to their sideboard and do not have to swap one for one, but after sideboarding, their
sideboard may not exceed the maximum sideboard size (10 battle cards).
Source: Wizards of the Coast (2019-11-21)    【Link to Ruling】
Tags: Sideboarding
During sideboarding, if I want to swap a character for a stratagem, when does that happen?

When you change your characters. You present your starting team (including stratagems) before swapping battle cards.
Source: Aequitas (2022-09-15)    【Link to Ruling】
Tags: Sideboarding
Regarding sideboarding, can I side out a combination of characters and star cards for 1 other character?

Yes. You absolutely could side out, for example, two characters and 3 star battle cards to bring in a bigger character from your sideboard. Just be sure after siding, your sideboard does not contain more than 10 battle cards and/or stratagems.
Source: Aequitas (2023-07-05)    【Link to Ruling】
Tags: Sideboarding