Are spiders invertebrates?

Yes.

To qualify as invertebrates the animal must not have backbones or an internal skeleton.

Since spiders do not have backbones or internal skeletons (they have an exo-skeleton), they are invertebrates.

Only bony fish, amphibians, reptiles, birds, and mammals have backbones and are, therefore considered, vertebrates. The other 98% of all animals on earth, in terms of numbers of species types, are invertebrates.

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No, a spider is not considered to be an invertebrate. A spider is a part of the arachnid family.