Answer
Cold Observables: Start producing values on subscription (e.g., HTTP calls).
Hot Observables: Produce values regardless of subscribers (e.g., events, websockets).
Cold = fresh execution per subscriber; Hot = shared execution.
Quick Answer
Cold observable: starts executing when subscribed, each subscriber gets their own execution (e.g., HttpClient - each subscribe makes a separate HTTP call). Hot observable: executing regardless of subscribers, all subscribers share the same execution (e.g., mouse events, WebSocket). Important distinction: subscribing to a cold HTTP Observable twice makes two HTTP requests. Use shareReplay() to make cold observables hot.
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SugharaIQ Editorial Team
Verified Answer
This answer has been peer-reviewed by industry experts holding senior engineering roles to ensure technical accuracy and relevance for modern interview standards.
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Source: SugharaIQ