Base62 vs MD5 for Short Code Generation

Compare two approaches for generating short codes: (A) Hash the long URL with MD5 and take the first 7 characters, (B) Use an auto-incrementing counter and encode it in Base62. Which approach is better and why?

Solution PathTarget: 8 min

MD5 hashing seems intuitive but introduces collision risk and retry complexity. Base62 encoding of an auto-incrementing counter is simpler, faster, and guarantees uniqueness with zero collisions.

01Two Approaches

1/4

We compare two approaches for generating 7-character short codes: (A) MD5 hash of the long URL, truncated to 7 characters, vs (B) auto-incrementing counter encoded in Base62.

MD5 Hashing vs Base62 Counter: which is better for short code generation?

02MD5 Hashing Analysis

2/4

MD5 produces a 128-bit (32 hex character) hash. Truncating to 7 characters loses information and creates collision risk. You must check the database before every insert and retry on collision, adding latency and complexity.

MD5: 128-bit output truncated to 7 chars. Collisions inevitable. Requires DB check + retry on every write.

03Base62 Counter AnalysisKEY INSIGHT

3/4

An auto-incrementing counter maps each ID to exactly one unique Base62 string. 62^7 = 3.5 trillion unique codes. Zero collision probability by design. No DB check needed before insert. Simpler, faster, and more predictable.

Base62 Counter: zero collisions, 62^7 = 3.5T capacity, O(1) encode, no DB check needed

04Final Verdict

4/4

Base62 counter wins on every dimension: simplicity, performance, and correctness. The only advantage of MD5 (deterministic deduplication of identical URLs) can be handled separately with a lookup index.

Base62 counter is the clear winner. Simpler, faster, collision-free, and predictable.

Concepts from this question1 concepts unlocked

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Base62 Encoding

EASY

An encoding scheme using 62 characters [a-zA-Z0-9] to convert numeric IDs into compact alphanumeric strings. Each character represents a digit in base-62.

62^n \text{ unique codes for } n \text{ characters} \implies 62^7 \approx 3.5 \times 10^{12}

Base62 maps auto-incrementing IDs to short, URL-safe strings with zero collision probability. It is the preferred encoding for most URL shortener designs.

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