Title case depends on the style and the sentence
MLA leaves prepositions such as through lowercase inside a title. Chicago capitalizes longer prepositions. Both capitalize the first and last word of a title or subtitle and its principal words.
Review each word shows the suggestion and its reason. A word such as up can be a preposition or part of a verb; change its choice when the suggestion does not fit your sentence. Existing API and iPhone capitalization can stay as you typed it.
A worked example
MLA gives A Walk through the Garden; Chicago gives A Walk Through the Garden. The words and punctuation stay in the same order.
Before you use the result
These are English title-case suggestions, not a grammar check or a citation formatter. Check names, phrasal verbs, foreign-language titles and unusual compounds. AP and APA styles are not offered.