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AWS S3 Key Length Limit | (Explained)

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The AWS S3 resource provides an amazingly powerful and scalable means of storing data in the cloud, but the approach that Amazon takes with the system isn’t the most intuitive at first glance.

While setting up an S3 storage bucket isn’t as complex as doing the same on a Linux OS server, it does take some understanding of how the S3 system works.

And that includes understanding how the AWS S3 key functions in particular.

What is the maximum AWS S3 Key Length Limit?

Generally, the largest an S3 filename can be per system limitation is 1,024 characters long.

These are saved in a UTF-8 format, and anything beyond that length of a name is truncated automatically when the S3 bucket key name is saved after first creation.

What is the maximum S3 bucket name length?

For the bucket itself, where data is stored, the name has to be at least 3 digits and no more than 63. They can be alpha, numeric or special characters.

Most folks with a need for more than one bucket develop a nomenclature so they can tell one bucket from the other, especially when lots of data is being stored and differentiation is a must.

A key point to remember, though, is that in addition to length, the name also needs to be in lower-case. It can include dashes, numbers and period dots.

Is S3 a key value store?

Yes, it does function as a key-value store in the Amazon system.

This is part of the function that allows AWS to store data in large sizes, without structure or with partial structure. It is also a differentiator in AWS’ NoSQL system. All objects added in get a unique key identifier.

That identity functions as a string, and it can be pretty much what someone wants it to be for labeling, tagging and database sorting.

What is the key in S3?

The key serves as a unique flag for the data object itself saved in the S3 bucket.

If, for example, the data is an image, the object key will identify the image in a unique manner so that it’s not duplicated by any other file or data set in the AWS system.

The metadata associated with the object key operates as a name-value pair set, describing the object. This unique labeling helps the AWS system find data and connect it quickly with other AWS resources.

What are valid key names when using AWS S3?

Acceptable key names can be any combination of UTF-8 characters. It’s a smart idea not to get too esoteric or creative with odd characters, as programs and systems that are going to be connected with AWS resources may not be as compatible or flexible in understanding all the symbols used.

Sticking to alpha-numeric based key names tends to be a practical approach. Special characters like exclamation symbols and parentheses are usable as well.

Other characters that are often confused in programs for other purposes, such as the @ symbol and the ampersand, dollar sign and colon should be avoided.

What is the maximum size of S3 object metadata?

The largest data size an S3 object metadata can be is extremely small at 2 kb. There’s supposed to be enough space to just add a basic description and no more.

What are AWS S3 file name limitations?

The file name, as noted above, should not be longer than 63 characters and no smaller than 3, the alpha characters should be in lower case, the beginning character and the last character has to be some kind of an alpha or numeric symbol.

The name definitely should not look or appear like an IP address, and it should also not start with a dash, colon, period or some other special symbol.

In addition, the name should be unique in the partition its operating. In other words, two S3 buckets can’t have the same name in the same AWS region or region grouping (higher level than just a region alone).

The AWS S3 key allowed characters include?

For the S3 object key, the characters must be Unicode, limited to 1,024 bytes in total length, and are compatible with UTF-8 character libraries.

With that said, there are more UTF8 characters possible than are practical. Generally, alphanumeric characters are a good, safe bet to use. Special characters such as the period, parentheses and asterisks can be used as well.

Dashes and slashes are often used to break up segments within an object’s key name for personal identifiers. However, symbols that are commonly used in programming such as the dollar sign, ampersand, equals, and the @ symbol should be avoided.

Can an AWS S3 Key with Spaces Occur?

Again, all normal UTF-8 characters are usable, but the name does need to be in a continuous sequence without gaps in the middle, i.e. spaces.

Dashes or slashes can be used as internal name separators, but a blank space will get kicked back by the AWS system as an invalid name format. Many folks instead use an underscore for a similar look and appearance, similar to Linux-style file naming.