までに details

write + by the time

kaku made ni

by the time; no later than — a deadline the action must land inside

meaning: by the time you write

明日あした出るでるまでに、部屋へやを片付かたづけてね。

ashita deru made ni, heya o katazukete ne.

Tomorrow, by the time you leave, tidy up your room, okay? casual

今月末こんげつまつまでに、レポートを提出ていしゅつしなければならない。

kongetsumatsu made ni, repooto o teishutsu shinakereba naranai.

I have to submit the report by the end of this month. neutral

Examples

by the time; no later than — the action must be complete before the marked point, once, not spread across it

明日あした出でるまでに、部屋へやを片付かたづけてね。

ashita derumadeni, heya o katazukete ne.

Tomorrow, by the time you leave, tidy up your room, okay? casual

今月末こんげつまつまでに、レポートを提出ていしゅつしなければならない。

kongetsumatsu made ni, repooto o teishutsu shinakereba naranai.

I have to submit the report by the end of this month. neutral

五時ごじまでに戻もどってきてね。

goji made ni modotte kite ne.

Be back by five, okay? casual

恐おそれ入いりますが、来週らいしゅう金曜日きんようびまでにご返信へんしんいただけますでしょうか。

osoreirimasu ga, raishuu kin'youbi made ni go henshin itadakemasu deshou ka.

I'm sorry to trouble you, but could you reply by next Friday? formal

Without に, まで alone marks a continuous "until" instead — this entry
does not cover bare まで.

うちに
うちに frames its limit as a closing window you must beat before an unwanted change locks in (暗くならないうちに), usually with urgency; までに just states an objective deadline point the action must land inside (五時までに), with no claim that anything is about to change for the worse.
まえに
まえに just orders two events, earlier before later, with no bound on how much earlier (何年前でもいい); までに fixes an actual deadline the action must land inside by, and typically pairs with an obligation or request in the main clause (提出しなければならない) that まえに never requires.