How do I say 'haha / lol'?

Chinese digital laughter has its own rich vocabulary, and the choice of laughter word communicates as much as the laughter itself:

• 哈哈 — genuine laughter. The more 哈, the funnier: 哈哈哈 is a real laugh, 哈哈哈哈哈哈 is crying with laughter. Safe in all contexts.
• 笑死了 / 笑死我了 — “dying of laughter.” The strongest everyday reaction. Reserved for things that are actually very funny; overusing it dilutes it.
• 笑死 (short form) — the casual “lmao.” Very common in group chats and social media.
• 呵呵 — the danger zone. Originally a pleasant chuckle, 呵呵 has been thoroughly sarcasm-poisoned by Chinese internet culture. Using it now reads as passive-aggressive, dismissive, or cold. Avoid unless you intend that tone.
• 嘻嘻 — playful, cheeky laughter. Often used by younger women. Cute rather than hilarious.
• 嘿嘿 — sly or mischievous laughter. “Heh heh.” Can be playful or slightly creepy depending on context.

The number of 哈 matters: 哈 = polite acknowledgment, 哈哈 = that was funny, 哈哈哈 = genuinely laughing, 哈哈哈哈 or more = this killed me. This granularity is a feature of Chinese digital communication that has no English equivalent.