DNS propagation is the process by which updates to a domain’s DNS records (A, AAAA, CNAME, MX, TXT, etc.) spread across the global network of DNS servers. When you change a record at your authoritative DNS provider—say, pointing “www” to a new IP address—that update doesn’t instantly reach every recursive resolver or ISP cache. Instead, each resolver holds a copy of the record for the duration of its Time-To-Live (TTL). Only when the TTL expires will that resolver ask the authoritative server for fresh data, then cache the new value.
Key points:
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Authoritative update: You modify your DNS records at the source.
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Zone refresh: Your DNS host publishes the new zone file; most update within seconds or minutes.
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Cache expiration: Public and private resolvers (e.g., Google DNS, ISP DNS) discard the old record after its TTL lapses.
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Recursive lookup: Upon receiving a query, a resolver without a valid cache entry fetches the latest data and then serves it.
Because TTLs often default to 1 hour (3 600 s) or more, full propagation can take up to 48 hours in extreme cases. To speed transitions:
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Lower your TTL to 300 s at least 24 hours before changes.
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Flush local DNS caches on your computer or router.
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Test against multiple public resolvers (e.g.,
dig @8.8.8.8,@1.1.1.1).
Understanding propagation avoids surprises: your website or email may still point to old servers until caches expire globally.
