# Snowflake ID
Snowflake IDs are 64-bit identifiers designed by Twitter for distributed systems requiring high-throughput, time-sortable ID generation.
## Overview
| Bits | 64 |
| Sortable | Yes |
| Timestamp | Yes (millisecond precision) |
| Format | Decimal integer |
| Coordination | Required (machine/datacenter IDs) |
## Format
```
1234567890123456789
```
### Bit Structure (Twitter format)
```
| Sign | 1 | Always 0 (positive) |
| Timestamp | 41 | Milliseconds since epoch |
| Datacenter ID | 5 | 0-31 |
| Worker/Machine ID | 5 | 0-31 |
| Sequence | 12 | 0-4095 per millisecond |
## Characteristics
### High Throughput
- 4096 IDs per millisecond per worker
- 4,096,000 IDs per second per worker
- With 32 workers: ~131 million IDs/second
### Time-Sortable
IDs generated later have higher values:
```bash
$ idt gen snowflake
1234567890123456789
$ idt gen snowflake
1234567890123456790 # Greater value
```
### Compact
64 bits fits in a single long integer in most languages.
### Requires Coordination
Unlike UUIDs, Snowflake IDs require assigning machine/datacenter IDs to avoid collisions.
## Generation
```bash
# Default Snowflake
idt gen snowflake
# With machine ID
idt gen snowflake --machine-id 1
# With datacenter ID
idt gen snowflake --datacenter-id 2
# Both
idt gen snowflake --machine-id 1 --datacenter-id 2
```
### Custom Epochs
Different systems use different epochs:
```bash
# Twitter epoch (default): Nov 4, 2010
idt gen snowflake --epoch twitter
# Discord epoch: Jan 1, 2015
idt gen snowflake --epoch discord
# Custom epoch (milliseconds since Unix epoch)
idt gen snowflake --epoch 1420070400000
```
### Environment Variable
Set default epoch via environment:
```bash
export IDT_SNOWFLAKE_EPOCH=discord
idt gen snowflake
```
## Inspection
```bash
$ idt inspect 1234567890123456789
SNOWFLAKE
1234567890123456789
Time 2023-01-15T12:34:56.789Z
Datacenter 1
Worker 2
Sequence 789
Hex 112210f47de98115
Base64 ESIQr0fpgRU=
Int 1234567890123456789
```
## Common Epochs
| Twitter | Nov 4, 2010 | 1288834974657 |
| Discord | Jan 1, 2015 | 1420070400000 |
| Instagram | Jan 1, 2011 | 1293840000000 |
## Comparison with Other IDs
| Bits | 64 | 128 | 128 |
| Sortable | Yes | No* | Yes |
| Timestamp | Yes | No* | Yes |
| Coordination | Required | No | No |
| Throughput | Very high | High | High |
*UUIDv7 has timestamp and sortability
## When to Use Snowflake
**Good for:**
- High-throughput systems (>100k IDs/second)
- Distributed databases
- Systems needing 64-bit IDs
- Real-time analytics (time-ordered)
**Consider alternatives if:**
- You can't coordinate machine IDs (use ULID)
- You need 128-bit IDs (use UUID or ULID)
- You're generating IDs client-side (use NanoID)
## Implementation Notes
### Machine ID Assignment
In production, assign machine IDs via:
- Configuration files
- Environment variables
- Service discovery (e.g., ZooKeeper, Consul)
- Database sequences
### Clock Skew
Snowflake IDs are sensitive to clock skew:
- Use NTP synchronization
- Some implementations wait for the clock to catch up
- Consider using UUIDv7 if clock skew is a concern
### Epoch Selection
Choose an epoch close to your system's start:
- Maximizes the timestamp range
- Twitter's epoch gives ~69 years from 2010
- A 2024 epoch would give ~69 years from 2024
## Variants
Different systems use slightly different bit layouts:
| Twitter | 41 | 10 (5+5) | 12 |
| Discord | 42 | 10 (5+5) | 12 |
| Instagram | 41 | 13 | 10 |
## Specification
- Original announcement: https://blog.twitter.com/engineering/en_us/a/2010/announcing-snowflake
- Wikipedia: https://en.wikipedia.org/wiki/Snowflake_ID