So, this expression has been around since the 1950’s and it goes in and out of use. It’s getting a little more use lately, but is still uncommon usage. The phrase refers to a high expectation for something that is, in reality, a great disappointment. Think of expecting a juicy hamburger, biting in, and finding out that there was no meat. Example: The party was supposed to be the event of the year, but it was a nothing-burger. Personally, as a native speaker, I would not use it as there are better and more common terms. It’s just not that common.

Never heard this word in 36 years :) maybe it’s British slang?

No, "nothing burger" is not a common word. It is slang that is meant to convey sarcasm or disappointment, but it is rarely used in everyday speech. I think the term became popular within the political scene after a conservative leaning group called "Project Veritas" secretly filmed a CNN news anchor by the name of Van Jones using the term to describe a lack of evidence connecting Donald Trump to Russian election interference. The example you used would be correct if you were expecting the file to be unpredictable and exciting. In other words, the file would be a "nothing burger" if it turned out to be different from what you wanted it to be and you felt disappointed. Here are some more example of how you could use the term "nothing burger". - The police raided the house in search of drugs, but they didn't find any. The operation was a nothing burger. - The man suspected his girlfriend of cheating on him, so he followed her around for a whole day. It turned out she wasn't cheating and the whole situation was a nothing burger. - I've been playing the lottery for many years, but I never win. All the money I've spent on lottery tickets has amounted to a big nothing burger.

Hi Atsumi, “Nothingburger” is a fun expression, but I don’t hear it used very often. When I do hear it used, it’s usually in the context of disappointment or sarcasm. Like “Well, that meeting was a big nothingburger 🤷🏻‍♀️” I think you used it just fine in that sentence.

Not very common and I have never heard anyone use it yet. I am British. I would just say that the subject lacks any substance or is meaningless.