によって / による

1. 1Marks the cause of an outcome or the agent in a passive sentence: 'due to', 'caused by', 'by'.Ex. 1
2. 2Shows that something differs or changes depending on the noun: 'depending on', 'varies by'.Ex. 2
3. 3Marks the means or method by which something is done: 'by means of', 'through'.Ex. 3

Common in both speech and writing, and especially frequent in news, reports and explanations. The 'depending on' sense normally pairs with predicates of variation such as 違う, 異なる or 変わる. Compared with ために, which covers reason and purpose generally, によって points to the specific cause or means behind a result.

• 1.
  に基づいてN2「に基づいて」means acting or judging on the basis of grounds such as data, facts, or rules, and leans toward written style; 「によって」does not emphasize such grounds. When you act 'based on regulations or documents,' use 「に基づいて」— it should not be replaced with 「によって」.
• 2.
  次第だ / 次第でN2These overlap only in the 'varies depending on...' sense: 「次第」stresses that success or failure hinges entirely on the preceding item, can take a 「かどうか」clause, and has a more everyday tone, while 「によって」focuses on stating that situations differ. 「次第」cannot express cause, means, or the passive agent.
• 3.
  に応じてN2「に応じて」is close to 「によって」only in the 'varies depending on...' sense: it stresses adjusting in line with the amount or degree of the preceding item, and what follows is typically a way of handling things. It cannot express cause, means, or the passive agent, and it also has separate senses of accepting an invitation or responding to a call.
• 4.
  ためにN4「ために」and 「によって」are similar only when expressing cause, where they are often interchangeable. However, 「ために」can also follow verbs and adjectives and can express purpose ('in order to'), while 「によって」attaches only to nouns and never expresses purpose.
• 5.
  せいでN3These are similar only for expressing cause: 「せいで」carries a blaming, dissatisfied tone and is used for bad results, whereas 「によって」is objective and carries no negative coloring. 「せいで」can follow verbs and adjectives, while 「によって」attaches only to nouns.
• 6.
  に照らしてN1「に照らして」means measuring something against a yardstick such as law, common sense, or experience, and what follows is typically a judgment or disciplinary action; it is a written-style expression. 「によって」expresses cause, means, the passive agent, or 'varies depending on...', with no sense of comparison, so the two generally cannot be interchanged.

によって marks cause, means, agent or variation. By contrast, に基づいて and に照らして give a basis or standard of judgment, 次第で stresses that an outcome hinges on how X turns out, and に応じて means adjusting in response to X; among the cause patterns, ために gives a general reason or purpose, while せいで blames a cause for a bad result.