Fallout 4 Quests

Quest system overview
Fallout 4 features an expanded quest system compared to previous Fallout games. In addition to the usual main quest, side quests and miscellaneous quests, the game includes a randomized quest system known as the Radiant quest system. These radiant quests use randomized characters, locations, and other elements and can be often be repeated indefinitely. The game's DLCs also include their own selection of main, side, miscellaneous, and radiant quests, which can be completed at almost any point during or after the main story and can even interact with the main quest in some ways.

Also unlike previous installments, the game does not end after reaching the end of the main quest. Instead the game continues with new post-game content, with the outcome of the main quest having a visible impact on the game world. This, combined with the infinite radiant quests and lack of a level cap, significantly extends the potential length of the game.

Prologue
The main story begins at the Sole Survivor's pre-war home in Sanctuary Hills, just minutes before the Great War.

Act one
Act one begins when the Sole Survivor awakens in the year 2287, 210 years after entering their cryo pod in Vault 111.

Act two
The beginning of act two is heralded by the arrival of the Prydwen, opening up the majority of the Brotherhood of Steel quests.

Act three
Act three begins when the Sole Survivor acquires the ability to fast-travel to and from the Institute at the end of Institutionalized. At this point, the main quest's structure splits into four different branches, one for each of the four main factions. Certain events in those factions' quests can make other factions hostile to the Sole Survivor, thus locking them from those branches and failing all of that faction's on-going quests. In some situations, this can be delayed (or even accelerated) with certain actions or certain dialogue choices.

Should the player character decide to oppose the Institute by supporting any of the other three factions, the main quest ends with the Nuclear Option quest (there are actually three variants of the same quest, one for each faction opposing The Institute). However, should the Sole Survivor join and support the Institute, the main quest ends with the Nuclear Family quest.

The following quests become available after completing Institutionalized:
 * Synth Retention (The Institute branch) - Starts automatically.
 * From Within (Brotherhood of Steel branch) - Given by Elder Maxson if the player character completed Show No Mercy, or was already given if they used the Brotherhood of Steel to advance in the Molecular Level.
 * Inside Job (The Minutemen branch) - Given by Sturges if the player character completed Old Guns, or was already given if they used the Minutemen to advance in the Molecular Level.
 * Underground Undercover (The Railroad branch) - Given by Desdemona if the player character joined the Railroad by completing the Tradecraft quest, or was already given if they used the Railroad to advance in the Molecular Level.

The Minutemen
The Minutemen quest line begins when the Sole Survivor meets Preston Garvey in Concord, and interacts closely with the settlement building system throughout.

Brotherhood of Steel
The Brotherhood quest line begins when the Sole Survivor encounters Recon Squad Gladius at Cambridge Police Station, and opens up significantly in the second act with the arrival of the Prydwen.

The Railroad
The Railroad quest line begins with the Sole Survivor following the Freedom Trail to Railroad HQ.

The Institute
The Institute quest line begins as the Sole Survivor successfully infiltrates the Institute with the signal interceptor at the end of the second act.

Secondary quests
These quests are not affiliated with any main faction.

Miscellaneous quests
These quests are displayed under the "Miscellaneous" section of the Pip-Boy.

Unmarked quests
These are quests that can be completed for certain rewards, but do not appear in the Pip-Boy.

Companion quests
The following quests are given once the player character gains enough affinity with a particular companion.

Automatron
These quests are only available after Automatron has been installed. 

Far Harbor
These quests are only available after Far Harbor has been installed. 

Vault-Tec Workshop
These quests are only available after Vault-Tec Workshop has been installed. 

Nuka-World
These quests are only available after Nuka-World has been installed. 