Is swallowing saliva break the fast?

 If he is aware of that, he should not swallow it deliberately; rather he should spit it out. If he is not aware of that, and he swallows his saliva as usual, then he realises what happened, it does not matter, because he did not do it deliberately.

 This is like one who rinses his mouth and nose, and something reaches his throat without him intending it to, or one who coughs or vomits without intending to. This does not affect his fast; rather what affects the fast is deliberately swallowing sputum or blood that reached his mouth, or deliberately swallowing food in his mouth. This is what affects the fast. 

But if he did not do that deliberately – rather he could not help it, and he did not do it deliberately – this does not affect his fast."

Complete Answer: https://islamqa.info/en/answers/293609/does-swallowing-ones-saliva-break-the-fast-if-it-has-been-changed-by-the-colour-or-smell-of-food