🚨 Redis Error Guide: 'ERR value is not a valid float' — Fix INCRBYFLOAT and Sorted-Set Scores

Overview

Redis returns value is not a valid float when a floating-point command is asked to parse something that is not a number it accepts. It shows up on INCRBYFLOAT, HINCRBYFLOAT, and ZADD/ZINCRBY scores — either because the stored value cannot be read as a float, or because the increment/score you supplied is not a valid float.

The literal error clients receive:

(error) ERR value is not a valid float

This is the float cousin of value is not an integer or out of range. Common culprits: a value written with a locale comma (3,14), leading/trailing whitespace, an empty string, or NaN/Inf where finite numbers are required.

Symptoms

• INCRBYFLOAT/HINCRBYFLOAT fails while a plain GET returns the key fine.
• ZADD key <score> member fails with a score that “looks” numeric to a human.
• Started after data was imported from a locale that uses , as the decimal separator.

redis-cli SET price "12,50"
redis-cli INCRBYFLOAT price 1.0

(error) ERR value is not a valid float

Common Root Causes

1. Stored value is not float-parseable

The existing key holds text, a comma-decimal, or trailing characters ("12.50 USD").

redis-cli GET price

"12,50"

2. The increment/score argument is malformed

redis-cli INCRBYFLOAT counter "1,5"     # comma, not dot
redis-cli ZADD leaderboard "" alice     # empty score

3. NaN or Infinity supplied

ZADD/ZINCRBY accept +inf/-inf as scores but reject nan; an INCRBYFLOAT that would produce nan/inf is rejected too.

redis-cli ZINCRBY leaderboard nan alice

(error) ERR value is not a valid float

4. Hidden whitespace or Unicode digits

A trailing \r, a non-breaking space, or full-width digits from a bad import will not parse.

How to diagnose

Step 1: Read the raw stored value

redis-cli GET price
redis-cli TYPE price

If it prints "12,50", "12.50 USD", or an empty string, that is the problem.

Step 2: Reveal hidden characters

redis-cli --no-raw GET price

"12.50\r"

--no-raw shows escape sequences like \r or embedded quotes that a normal print hides.

Step 3: Test the argument in isolation

redis-cli SET tmpfloat 0
redis-cli INCRBYFLOAT tmpfloat 1.5    # confirm a clean float works
redis-cli DEL tmpfloat

Step 4: For sorted sets, check the score you are sending

redis-cli ZADD testset 3.14 member   # valid
redis-cli ZADD testset 3,14 member   # invalid -> the error

Fixes

Normalize the stored value to a dot-decimal number

redis-cli SET price "12.50"
redis-cli INCRBYFLOAT price 1.0

"13.5"

Send increments/scores with a dot decimal, no thousands separators

redis-cli INCRBYFLOAT counter 1.5
redis-cli ZADD leaderboard 100.25 alice

Sanitize input at the application boundary

Trim whitespace and convert locale commas before writing:

raw = user_input.strip().replace(",", ".")
r.set("price", float(raw))   # store a clean numeric string

Use +inf / -inf intentionally, never nan

redis-cli ZADD leaderboard +inf vip      # allowed

What to watch out for

• Redis stores numbers as strings; a value that “looks” numeric can still carry invisible bytes. Always check with --no-raw when parsing fails.
• INCRBYFLOAT results are formatted without trailing zeros (13.5, not 13.50) — don’t rely on fixed decimal places.
• Sorted-set scores are IEEE 754 doubles; extreme magnitudes lose precision even when they parse.
• Bulk imports from spreadsheets are the top source of comma-decimal values; validate during ingestion, not at read time.

Related

• Redis Error: ‘value is not an integer or out of range’
• Redis Error: ‘increment or decrement would overflow’
• Redis Error: ‘WRONGTYPE Operation against a key holding the wrong kind of value’

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