The traditional rule: use shall with I and we for the plain future, and will for the other persons — reversing them to show determination. Almost nobody follows it now. In modern English will is standard throughout, and shall survives mainly in offers and suggestions ("shall we?") and in legal drafting.
The core difference
A rule that was always more prescribed than observed, and is now largely historical.
- traditional — I shall, you will for the plain future; reversed for determination (I will = I insist).
- modern — will throughout; shall for offers and questions: Shall I open a window?
- legal — shall for obligation: the tenant shall maintain the property.
The legal problem
Shall in drafting is meant to impose a duty, but courts have interpreted it inconsistently for exactly that reason. Plain-language drafting guides now recommend must instead, which nobody can misread. That is a genuine shift in professional practice rather than a stylistic preference.
What survives naturally
Shall is alive and idiomatic in first-person questions — Shall we go?, Shall I help? — where will would sound like a prediction rather than an offer.
Frequently asked questions
Is the shall/will rule still taught?
Rarely, and it was never consistently observed. Modern usage uses will throughout.
Where does shall still belong?
In offers and suggestions — "shall we?" — and traditionally in legal drafting, though plain-language guides now prefer "must".
Why do legal guides prefer must?
Because courts have interpreted shall inconsistently, while must unambiguously imposes an obligation.