Is it bad to mix Spanish from different countries?

No, it's not bad. Almost every learner ends up mixing a bit, since podcasts, shows and teachers come from different countries. Native speakers will understand you, and most won't mind. The only thing worth keeping consistent is a few choices within a single conversation, like your word for "you".

Why mixing happens

You learn from a teacher from Spain, watch Mexican shows and listen to Argentine music. Your Spanish naturally picks up pieces from all of them. That's completely normal, and plenty of native speakers who've moved around do the same.

Spanish is also well-standardized. The core grammar is shared, and most words are the same everywhere, so mixing rarely causes confusion.

What native speakers think

Most Spanish speakers are used to hearing other accents, because of TV, music and travel. If you use a word from another country, they might smile or ask what you mean, and that's usually the extent of it.

A few exceptions come up:

• Vulgar or regional words. Some words are harmless in one country and rude in another. Coger is the classic example. It's an everyday verb in Spain but vulgar in much of Latin America. When in doubt, use a neutral word like tomar or agarrar.
• Local slang. Using Argentine or Mexican slang in the wrong place can sound odd. Not offensive, just out of place.

What to keep consistent

A mix is fine, but within one conversation a few things should line up:

1. How you say "you". Don't switch between tú, vos and vosotros in the same chat. Pick the one that fits the person. See tú vs usted.
2. Verb forms with that pronoun. If you use vos, use tenés. If tú, use tienes.
3. Pronunciation of z and c if you can. You don't have to, but mixing "th" and "s" in the same sentence will sound strange. Even then, people will understand.

How to decide on a main variety

I suggest picking a main variety as your base, the one you'll use most, and letting the rest be "listening Spanish". You understand them, but you don't have to speak them. For help choosing, see Spain or Latin American Spanish.

Extra listening is easy to collect if you already open your phone every day. Langtok, my app, has short Spanish stories you swipe through with word-by-word subtitles and a slow-down option.

Adapt when you can

If you're talking to someone from a specific country, you can borrow a few of their words and expressions. People like that. If you're in Mexico, say celular instead of móvil. In Spain, use vosotros with friends. It's a small effort that shows respect.

The bottom line

Don't worry about "pure" Spanish. There isn't one. Focus on being understood, keep your "you" forms consistent, and avoid words you aren't sure about. Your Spanish will settle into a personal style over time, and that's exactly what native speakers have too.