Synth Synth is a diminutive for synthetic humanoid and is used to name designed by the Institute to look , function and behave like human s . They are sometimes also called androids or artificial humans . They are found in the Capital Wasteland in 2277 and in the Commonwealth and the Island in 2287 . Background . Synths , created by the Institute , are cybernetic organism s designed to resemble humans . They are classified into one of three generations depending on their complexity : Nick Valentine and DiMA are unique synths , both being prototype synths intended to bridge the gap between the Gen 2 synths and the truly sapient Gen 3 synths . While DiMA was made to freely develop a personality from experience , Nick ' s personality was built upon the mind of a pre - War detective who volunteered to have his memories encoded , giving him all of the memories and experiences of his namesake . The two of them escaped the Institute together , but due to the limited memory space of their prototype brains , Nick ' s memory of the escape was deleted . This led him to believe that he was thrown out by the Institute . DiMA later traveled to the Island and founded the synth refuge of Acadia with Faraday . As DiMA reached the limit of remaining space in his prototype brain , he began to artificially increase his memory capacity by storing his memories in connected computers . Although it is unknown when each successive generation was developed , the people of Diamond City first encountered a synth in 2229 , in an event called the Broken Mask incident . The synth , which called itself Mr . Carter , was a prototype that was field tested without the Institute director ' s approval . Though the Institute did not actually intend to massacre the people of Diamond City , the people of Diamond City have feared and resented the Institute ever since . By 2277 , at least one Generation 3 synth is known to have had traveled to the Capital Wasteland after becoming fully self - aware and escaping the Institute . With the help of the underground organization known as the Railroad , he had his appearance and memories altered and eventually wound up as the chief of security at Rivet City . Incidents of synths escaping have occurred multiple times prior to 2277 as the Synth Retention Bureau was created and had multiple courser s tracking rogue synths as far as the Island . Many denizens of the Commonwealth have become paranoid and prejudiced against synths , fearing they might be abducted by the Institute and replaced with identical copies of themselves . Their paranoia is justified , as some of the most sophisticated synths encountered act as spies and could fool the unaware . There are some examples of Commonwealth citizens that were murdered and replaced with synth duplicates whom the Sole Survivor interacts with on missions if they choose to join the Institute . The synths ' Institute creators view them as nothing more than machines and treat them as slaves . The Railroad has committed itself to freeing Generation 3 synths from their masters and smuggling them out of the Commonwealth to somewhere the Institute cannot reach them . In contrast , the Brotherhood of Steel has sworn to eliminate all synths , for to them , a machine capable of thinking like a human is an abomination of technology . Most encountered hostile synths belong to either Generations 1 or 2 , are armed with Institute laser weapons and shock batons and are immune to radiation damage . When fighting against the Gen 1 and 2 synths , it is possible to shoot off their limbs . The moment one of their arms is destroyed , they may be unable to use their weapons . However , they will then proceed to rush the player character and begin attacking them with their remaining arm . Shooting their legs will result in them crawling to the player character and attacking them with their hands . Gen 1 and 2 synths are less intelligent than Gen 3 synths , but display a level of sapience , as exemplified in their dialogue . They call out to their target " whoever you are , I know you ' re there " and will comment that their systems may be in need of recalibration if they lose track of a target . During the Tradecraft quest , Deacon comments that Gen 1 and 2 synths are on a similar mental level to protectrons and other pre - War robots , causing some debate among members of the Railroad as to if Gen 1 and 2 synths are worth trying to rescue . Generation 3 synths are physically and mentally indistinguishable from ordinary humans , having lab - grown bodies of real human flesh , bones , and organs instead of plastic and metal . As Dr . Roslyn Chambers found , no medical tests or procedures can identify someone as a synth without killing them ( synths that infiltrate settlements , for example , only drop synth component s when killed ) . Psychological tests , such as Covenant ' s SAFE test , are dubious at best . However , they are not perfect duplicates , and have a few key differences from humans that are not immediately obvious : synths cannot gain or lose weight ( one Institute researcher remarked on this after discovering that many of the Institute synths had a taste for snack cakes ) . There are many Generation 3 synths that are hidden in plain sight in the Commonwealth . They include , but are not limited to , Magnolia , the singer of the Third Rail and Danse , a paladin of the Brotherhood of Steel . Gameplay . While most Synths are Gen 1 or Gen 2 and are thus allied to the Institute , synths can also be encountered in other places . If the player character has built a radio beacon , incoming settlers have the potential to be Gen 3 synths ( non - infiltration ) . If these settlers are put on a supply line and happen to pass any major Brotherhood of Steel encampment ( Cambridge , etc . ) they will be fired upon by the entire station , stalling any building the player character can do . Synths can also be a part of a Minutemen patrol if the Sole Survivor has retaken the Castle and has an ample amount of well - off settlements . If a Minutemen patrol that possesses these synths passes a Brotherhood encampment , they will not be fired upon . Sometimes their patrol routes take them straight through the Boston Airport , into the courtyard of Fort Strong , and back through again . They will not fire upon each other and will sometimes pleasantly engage in dialogue with each other . If the player character has established a bad reputation with the Institute ( in other words , completed the quest Banished from the Institute ) , the Sole Survivor ' s settlements will often be infiltrated by synths who will eventually open fire on the player character ' s other settlers . This will be a rare occurrence after the Institute is destroyed . Variants . Synth . Synths often come in groups of four or so , armed with Institute weapons . Like ghouls , their limbs can be removed without killing them , and they will adjust their tactics accordingly . Synth strider . Stronger than an ordinary synth , these striders , while fairly weak , are still a significant step up . They , like their counterparts , almost exclusively use Institute weapons and in some instances , shock batons . Synth leader . Unlike most synths , leaders are armored and possess heavily modified Institute weapons . They almost exclusively travel with other synths and often act as the final opponent in synth occupied areas . Synth patroller . A step up from the synth strider and leader variants , the patroller is stronger and has better aim . They are usually seen in groups with other synths , such as synth striders or leaders , and are usually seen with Institute pistols or rifles . Synth seeker . A variant even stronger than the synth patroller . As with other synths , they can be found traveling in groups . Usually seen with the same weapons as the synth patroller . Synth trooper . Synth troopers are the standard Institute soldier and more aggressive than most of their counterparts . They usually spawn in weaker packs of synth striders or occasionally patrollers . Synth stormer . The synth stormer is a high - level synth , often seen with other high - level variants of synths equipped with sturdy or heavy synth armor . Synth eradicator . The synth eradicator is the strongest variant of synth . Boasting strong weapons and armor , they are on par with Brotherhood knights . Appearances . Synths appear in " Fallout 3 " and " Fallout 4 " . The two synths encountered in " Fallout 3 " , Armitage and Harkness , were ostensibly Generation 3 synths , and Generation 1 and 2 synths were not introduced until " Fallout 4 " .