Evidence-based answer · Last updated · How it’s made
This is a general question about age effects in language learning, not something specific to French, so the honest answer is a general one: research consistently finds that starting younger gives an edge, especially for sounding native-like, but age is only one factor among many (motivation, amount of use, education, aptitude, quality of input), and adults can still reach very high, sometimes near-native, levels. None of the sources studied French learners specifically enough to say the age pattern works differently for French than for other languages.
Asked as someone learning French. Findings drawn from French-specific research are framed for French learners and may not hold for other languages; where the evidence is general second-language research, the report says so.
How much a person uses the language, their level of education in it, their motivation, their natural language-learning aptitude, and the quality of the input they get all substantially affect final proficiency — sometimes more than the age they started.1,3,6
Example
Multiple studies have found late learners (people who started as teenagers or adults) who perform indistinguishably from native speakers on certain language tests, showing native-like competence is achievable even without an early start, though achieving it on every single measure of language ability at once is rare.5,8,12,13
In one study comparing children who started a foreign language at age 8 versus age 12 in school, the early starters' advantage had mostly disappeared by age 18, except for children who were being raised bi-literate in two languages, suggesting that classroom-based early starts don't guarantee a lasting benefit the way early immersion might.3
People exposed to a language from birth or infancy don't automatically end up as strong in that language as people would expect; in one comparison, early-exposed heritage speakers of Greek scored far below both monolinguals and late learners who started around age 8, showing that age of first exposure alone doesn't determine outcome.7
If the goal is to sound as close to a native French speaker as possible on every dimension, starting as a child gives a real statistical edge, particularly for accent — but this comes from general second-language research, not French-specific studies, so treat it as a broad pattern rather than a French guarantee. If you're an adult starting French now, the sources suggest age is not destiny: focus on the things shown to matter alongside or instead of age — getting plenty of real use and exposure, pursuing education or structured study in the language, staying motivated, and seeking good-quality input (native speech, correction, and practice). Don't be discouraged from aiming for a very high level of grammar and fluency as an adult; the evidence that adults are 'doomed to fail' at grammar specifically is weak, even though pronunciation is the area where an accent is more likely to persist.
Now pick something to do it with
Each of these opens an overview of the apps, courses and immersion material worth a look for that — filtered to exactly what the advice above points you at:
Or see the full resource list