Synth designations[1][2] are 4-character identification codes used by synths developed by the Institute. Within the Institute they serve as a synth's name, and they are also used along with a recall code to initialize a factory reset.


Each synth designation is formatted as follows:

  • A is an alphabet character.
  • Xs are numbers in the range of 1 to 9.

An X typically designates a Courser, though A and Z designations also occur.

List of known synth designationsEdit

Designation Role Other names
A3-21 Escaped and memory wiped synth
Chief of security at Rivet City
B2-57 Escaped synth hiding at Bunker Hill
B5-92 Escaped and memory-wiped raider leader at Libertalia Gabriel
C2-41 Possibly memory-wiped synth last seen in Goodneighbor
F6-33 Escaped synth hiding at Bunker Hill
G5-19 Escaped, brain damaged synth being cared for in Goodneighbor Curie
G7-81 Escaped synth
Railroad Heavy
G9-81 Institute tunnel laborer shift manager (potentially escaped)
H2-22 Institute tunnel laborer (escaped)
J2-84 Malfunctioning synth within the Institute
J5-22 Escaped or destroyed missing synth
J9-04 Escaped synth Gametitle-FO4 CC Harold
K1-98 Runaway synth captured by Gunners Jenny
K3-19 Maintenance synth within the Institute
K8-23 Synth found destroyed by raiders
L3-37 Memory-wiped runaway synth last seen at Corvega assembly plant Leo
L7-92 Surface patrol member (escaped)
Far Harbor shopkeeper
M7-62 Synth double
Diamond City plant
M7-97 Escaped and memory wiped synth
Brotherhood of Steel paladin
PR-15 Escaped synth Gametitle-FO4 CC Carol Janssen
R3-11 Escaped synth Gametitle-FO4 CC Burner
S9-23 Child synth designed by Father Shaun
S9-43 Missing synth seen at Boston Airport
X1-91 Courser sent after synths
X2-36 Courser sent after C2-41
X2-71 Courser sent after synths
X3-24 Synth (presumably courser) operating the Institute's relay
X3-28 Synth (presumably courser) involved in SRB requisitions
X3-37 Courser sent after synths
X3-51 Courser sent after K8-23
X4-18 Courser sent to Bunker Hill after B2-57, F6-33 and Y9-15
X4-72 Malfunctioning synth (presumably courser) reassigned from SRB
X5-76 Courser sent after synths
X6-57 Synth (presumably courser) operating the Institute's relay
X6-88 Courser companion
X7-55 Courser sent after synths
X9-27 Courser sent to Ticonderoga safehouse
X9-73 Courser sent after L3-37
Y9-15 Escaped synth hiding at Bunker Hill
Z1-14 Synth escape organizer
Z2-47 Courser at Greenetech Genetics sent after K1-98
Z3-22 Escaped synth hiding at Bunker Hill

Atypical designationsEdit

Designation Role
A-2018 Institute defense
B-263 Courser found dead at Fairline Hill Estates Gametitle-FO4 CC
XPN-20A Institute defense

See alsoEdit


  1. X6-88: "Yes, sir. Designation X6-88."
    (X6-88's dialogue)
  2. X6-88: "Designation B5-92 is holed up in the shack on top of the up-ended cargo ship."
    (X6-88's dialogue)
Institute flag
Fo4 Institute Seal
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