À tout hasard means “just in case” or “on the off chance”. Word for word, à is “at”, tout is “any” and hasard is “chance”, so the phrase translates literally as “at any chance”. It describes an action taken as a precaution, without knowing whether it will actually be needed. The phrase does not introduce a clause of its own, unlike some of its alternatives, and can sit at the start, middle or end of a sentence.

A note on pronunciation

Hasard begins with an h aspiré, an aspirated h. French has two kinds of h at the start of a word: an h muet, which behaves like a vowel and allows liaison and elision, and an h aspiré, which blocks both. Because hasard falls into the second group, the final consonant of tout is not linked to it in speech, so tout hasard is pronounced with a clear break between the two words [AH TOO AH ZAR], not run together as it would be before a vowel. The same rule means the article does not shorten in front of it, giving le hasard [LEr HAH ZAR] rather than l’hasard.

Basic use

À tout hasard usually explains why someone did something without being sure it was necessary.

• J’ai pris un parapluie à tout hasard. – “I brought an umbrella just in case.”
• Je vous laisse mon numéro à tout hasard. – “I’ll leave you my number just in case.”
• Elle a gardé le reçu à tout hasard. – “She kept the receipt just in case.”
• Il a apporté des outils à tout hasard. – “He brought some tools just in case.”
• Prenons de l’eau à tout hasard. – “Let’s take some water just in case.”

Position in the sentence

The phrase can open a sentence as well as close it, with much the same meaning.

• À tout hasard, je vais vérifier encore une fois. – “Just in case, I’ll check one more time.”
• À tout hasard, appelle-moi si tu as besoin. – “Just in case, call me if you need anything.”
• À tout hasard, j’ai aussi apporté un plan B. – “Just in case, I also brought a backup plan.”

À tout hasard versus au hasard

Au hasard, without tout, means something quite different. It means “at random” or “randomly”, describing a choice made without any particular reason or method.

• Il a choisi un livre au hasard. – “He chose a book at random.”
• Elle a répondu au hasard. – “She answered at random.”

Adding tout changes the meaning from randomness to precaution, so the two phrases should not be mixed up.

À tout hasard versus au cas où

Au cas où also means “in case”, but it works differently. It normally introduces its own clause, with a verb in the conditional or future tense, and states the specific situation being planned for. À tout hasard is vaguer and does not spell out what the precaution is for.

• Prends un manteau au cas où il ferait froid. – “Take a coat in case it’s cold.”
• Prends un manteau à tout hasard. – “Take a coat just in case.”

The first sentence names the reason for the precaution. The second does not, and simply signals that the speaker is being cautious.

Synonyms and alternative expressions

• Au cas où – “in case”
• On ne sait jamais – “you never know”
• Par mesure de précaution – “as a precautionary measure”
• Par précaution – “as a precaution”
• Pour être sûr – “to be safe”

On ne sait jamais is often added alongside à tout hasard, as a short remark rather than a full clause, to underline that the outcome is uncertain.

• J’ai gardé le ticket, on ne sait jamais. – “I kept the ticket, you never know.”
• Je prends mon passeport à tout hasard, on ne sait jamais. – “I’m taking my passport just in case, you never know.”

Summary

À tout hasard means “just in case” or “on the off chance”, and describes a precaution taken without knowing whether it will be needed. It can appear at the start or end of a sentence and does not introduce its own clause. Au hasard, without tout, means “at random” instead, and should not be confused with it. Au cas où is a close alternative that spells out the specific situation being planned for, while à tout hasard leaves it unstated.