Introduction

If you want a non-cryptographic hash with a very low collision rate, the first thing to clarify is that no fixed-width hash can guarantee zero collisions for arbitrary input. What you can choose is a hash with good distribution, strong avalanche behavior, and enough output bits for your scale. In practice, the best answer is usually not "find a magical collision-free function," but "pick a proven fast hash and use a wide enough output."

What "Low Collision" Really Means

Collisions happen whenever two different inputs produce the same hash value. For a 64-bit hash, the output space is large, but not infinite. As the number of hashed items grows, collisions become more likely.

That means the right question is usually:

• how many items will you hash
• how uniformly must the hash distribute values
• do you need resilience against malicious inputs
• do you need 64-bit or 128-bit output

If the inputs are not adversarial and the goal is fast lookup, sharding, dedup hints, or partitioning, a good non-cryptographic hash is often the right choice.

Common Modern Choices

Several non-cryptographic hash families are widely respected for speed and quality:

• 'xxHash'
• 'MurmurHash3'
• 'FarmHash'
• 'CityHash'
• 'wyhash'

For many general-purpose applications today, xxHash and wyhash are common answers because they are fast and have good distribution properties.

If you need lower collision probability than a 64-bit output gives, use a 128-bit variant when available rather than over-optimizing the mixing function alone.

Example With xxHash

A small Python example using xxhash looks like this:

1import xxhash
2
3values = [b"alpha", b"beta", b"gamma"]
4for value in values:
5    h = xxhash.xxh64(value).hexdigest()
6    print(value, h)

If you want a wider digest:

1import xxhash
2
3value = b"alpha"
4h = xxhash.xxh128(value).hexdigest()
5print(h)

The move from 64-bit to 128-bit often matters more for practical collision risk than switching among several good hash families.

When Non-Cryptographic Hashes Are Appropriate

Use a fast non-cryptographic hash when you need:

• hash-table keys
• partitioning or sharding
• fast duplicate detection hints
• bloom filters or probabilistic data structures
• checks inside trusted systems where adversarial collision attacks are not a concern

These functions are designed for throughput and distribution quality, not for resisting deliberate attack.

When They Are the Wrong Tool

If users can choose inputs maliciously, a non-cryptographic hash may be the wrong answer. Attackers can exploit weaknesses in some hash families to force collisions or degrade performance.

In those cases, use a cryptographic hash or a keyed construction designed to resist adversarial input.

That is why the phrase "very low collision" should always be paired with context. For trusted internal workloads, a good non-cryptographic hash is usually enough. For untrusted public input, collision behavior is only part of the story.

Width Often Matters More Than Brand

People sometimes compare MurmurHash, xxHash, and similar families as if one name alone determines everything. In practice, output width and workload characteristics often matter more.

For example:

• a good 128-bit non-cryptographic hash is usually safer against accidental collisions than a good 64-bit one
• a high-quality 64-bit hash is usually more than enough for ordinary in-memory hash tables
• if collisions are extremely costly, you may need to store the original key or perform equality verification after hashing anyway

A hash is rarely the only line of defense against incorrect identity.

A Practical Selection Rule

A reasonable engineering rule is:

• choose xxHash or another well-regarded modern hash for fast general-purpose internal use
• choose 128-bit output when accidental collisions are especially expensive
• choose a cryptographic hash when inputs are adversarial or security-sensitive

That rule is more useful than chasing the idea of one universally best non-cryptographic hash.

Common Pitfalls

The most common mistake is asking a non-cryptographic hash to do a cryptographic job. Fast hashing and attack resistance are different design goals.

Another mistake is focusing only on the function name instead of the output width. A solid 128-bit hash often reduces practical collision risk more than switching between two good 64-bit hashes.

Developers also sometimes assume the hash alone guarantees uniqueness. If collisions are truly unacceptable, the system should verify the original keys or use a different identity model.

Finally, benchmarks matter. A hash that is ideal for tiny keys may not be ideal for large payloads or a specific CPU architecture.

Summary

• No fixed-width non-cryptographic hash can guarantee zero collisions.
• For low accidental collision rates, use a proven fast hash such as xxHash or another modern alternative.
• Prefer wider outputs such as 128-bit when collision cost is high.
• Use non-cryptographic hashes only when adversarial input is not the main concern.
• If collisions are truly unacceptable, verify the original keys or change the identity strategy.