Is the word ao the same in Brazilian and European Portuguese?

Yes.

The word ao is a contraction of the preposition a (to/at) and the masculine singular definite article o (the). In both Brazilian and Continental Portuguese, the spelling, grammatical function, and core meaning are identical. The only difference lies in pronunciation. In Brazilian Portuguese, the vowels tend to be more open and clearly articulated. In Continental Portuguese, the vowels are often more closed or reduced, meaning the "a" sound may be much more subtle or nearly swallowed in natural speech.

Brazilian Portuguese Examples

1. Eu estou indo ao shopping. (I am going to the mall.)
2. Ele entregou o documento ao chefe. (He handed the document to the boss.)
3. Vamos ao mercado agora. (Let's go to the market now.)
4. O cachorro correu ao lado do menino. (The dog ran beside the boy.)
5. Ele deu um presente ao seu namorado. (He gave a gift to his boyfriend.)

Continental Portuguese Examples

1. Estou a ir ao centro comercial. (I am going to the shopping center.)
2. Ele entregou o documento ao patrão. (He handed the document to the boss.)
3. Vamos ao supermercado agora. (Let's go to the supermarket now.)
4. O cão correu ao lado do rapaz. (The dog ran beside the boy.)
5. Ele deu um presente ao seu namorado. (He gave a gift to his boyfriend.)