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Smartphone carriers suggest texting, rather than calling, because it is more likely to go through. “So if they make a voice call, they may have to make a second attempt for it to go through,” Sprint spokeswoman Crystal Davis said. “So we recommend they text instead of call.”

If the networks get too congested, customers can also look for WiFi networks at coffee shops.

During the past inauguration, Twitter’s traffic increased fivefold, and in some cases, users noticed delays of up to five minutes.

Instagram, which was around in 2009, and YouTube are in for a particularly difficult challenge, because their websites rely on sharing photos and videos, which takes up much space, whereas Twitter relies on simple text.

“Instead of a 140-character tweet, it’s an entire photo or set of photos, which require much more data to share,” Mr. Dornfeld said. “So if you’re a spectator at the Mall trying to tweet about the event, that requires a smaller amount of data.”