Difference between Fallback and Default

Question

Is there a difference between these two or are they synonyms ?

Example: If x not in data --> use (default/fallback) value

Answer 1

The terms default and fallback are very similar in that they refer to a value used if some other value is not provided.

The difference is in the implication.

• fallback: you would prefer to use some other value, but if it is not available you can "fall back" to the fallback value. It is in the same vein as backup or contingency.

  • "something on which one can fall back : RESERVE —often used attributively

    a fallback career

    a fallback position"

    ~https://www.merriam-webster.com/dictionary/fallback

• default: you have no preference, the default is used unless some other value is provided.

  • "computers : a selection automatically used by a program in the absence of a choice made by the user" ~https://www.merriam-webster.com/dictionary/default

Personally, I use "default" unless I want to emphasize that this value should not normally be used.