BBEdit is pretty much the standard for opening large text files on a Mac. I've opened some good-sized files with it, and BBEdit didn't even break a sweat.

How large of a file are you talking about? And how much RAM does your Mac have (both installed and free)?

_{Edited to add…}

Bare Bones released BBEdit 9.6 today, and according to the Release Notes¹ (under Changes):

It is now possible to open files significantly larger than before; the ceiling isn't unlimited, but it is no longer limited by the previously extant constraints in the OS.

Sounds to me like it's worth upgrading (free for anyone with BBEdit 9.x) and trying again.

_{¹ If you've never read a Bare Bones release notice before, you should. Even if you have no interest in BBEdit. Even if you have no interest in Bare Bones. Even if you have no interest in text editors in general. They're that good. Yes, really. Iä! Iä! Pnoies fhtagn!}

BBEdit is pretty much the standard for opening large text files on a Mac. I've opened some good-sized files with it, and BBEdit didn't even break a sweat. It is not entirely free - you do not have to pay for a license unless you want features that are in the pro activation above and beyond the free license.

How large of a file are you talking about? And how much RAM does your Mac have (both installed and free)?

_{Edited to add…}

Bare Bones released BBEdit 9.6 today, and according to the Release Notes¹ (under Changes):

It is now possible to open files significantly larger than before; the ceiling isn't unlimited, but it is no longer limited by the previously extant constraints in the OS.

Sounds to me like it's worth upgrading (free for anyone with BBEdit 9.x) and trying again.

_{¹ If you've never read a Bare Bones release notice before, you should. Even if you have no interest in BBEdit. Even if you have no interest in Bare Bones. Even if you have no interest in text editors in general. They're that good. Yes, really. Iä! Iä! Pnoies fhtagn!}

BBEdit is pretty much the standard for opening large text files on a Mac. I've opened some good-sized files with it, and BBEdit didn't even break a sweat.

How large of a file are you talking about? And how much RAM does your Mac have (both installed and free)?

BBEdit is pretty much the standard for opening large text files on a Mac. I've opened some good-sized files with it, and BBEdit didn't even break a sweat.

How large of a file are you talking about? And how much RAM does your Mac have (both installed and free)?

_{Edited to add…}

Bare Bones released BBEdit 9.6 today, and according to the Release Notes¹ (under Changes):

It is now possible to open files significantly larger than before; the ceiling isn't unlimited, but it is no longer limited by the previously extant constraints in the OS.

Sounds to me like it's worth upgrading (free for anyone with BBEdit 9.x) and trying again.

_{¹ If you've never read a Bare Bones release notice before, you should. Even if you have no interest in BBEdit. Even if you have no interest in Bare Bones. Even if you have no interest in text editors in general. They're that good. Yes, really. Iä! Iä! Pnoies fhtagn!}