Why are these charts different?

Different brokers, same timeframe, same timespan across the graph. They remain nearly identical until one takes a sharp turn up and the other goes down.

I don’t think you’ve got two charts of the same pair up - the first chart is not USD/CHF today - it shows the latest price about 0.96640. USD/CHF has not been that high since June. Though I don’t recognise what it is.

Same currency pair. Both pictures taken seconds apart at approx 830am CST today.

Then must be a bad data feed from/via the broker.

Is that the only possible explanation? And how common of an occurrence is such a thing?

Not often, but I rarely go down to M1 time-frame.

Which trading platform is this…

The first is MT4 mobile app, the second is FOREX

The price of any pair at any moment should be the same across all brokers, right?

Well, like I said, I don’t get down to the M1 time-frame but on less frequent views of the longer time-frames its rare to see a difference of more than a pip or two.

The real price difference is often between daily opens as different brokers use different data sources and also different start times for this: e.g. my broker uses 2200hrs UK time as the end of today and start of tomorrow.

Hi,
Absolutely not the case. I cannot see the timescale or the price on the second screenshot (but I can see the pair USD/CHF on the second screenshot but not on the first. So I will take your word for it that they represent the same pair and the same timeframe. So the candles are one minute each. On the first screen (AT&T feed) the difference between the high of the wick 4 from the end and the low wick is 0.9651 to 0.9644 which is 7 pips. The time on your mobile phone is 08:48 and the time on your chart is 16:30, so you are 7.5 hours behind the timezone of your broker. It seems to me that your broker timezone is London, where market close is 16:30 hrs. If that is the case, I am not sure where you are located unless the time on your mobile phone is not correctly set West Coast time when you took these snapshots is 08:30am. In any event, just on market closure, expect the spread to widen. 7 pips high to low in one minute is not unusual at closing, and the assumption that all brokers quotes should be the same is erroneous. Brokers make their fees on spread, and slippage, and I suspect it is the latter that is causing the majority of the difference. In any event, unless you can post two images that show the same data, any answer is speculative. But a good question for learning.