🚨 Slack Error: 'invalid_name' — Cause, Fix, and Troubleshooting Guide

Overview

invalid_name means a name value you passed was rejected as malformed. It shows up most often on reactions.add (an invalid or non-existent emoji name) and on channel-creation/rename calls (a name that breaks Slack’s naming rules).

{
    "ok": false,
    "error": "invalid_name"
}

Symptoms

• reactions.add fails for one emoji but succeeds for standard ones.
• The emoji name was passed wrapped in colons, or with a skin-tone suffix, or is a custom emoji that doesn’t exist.
• Channel create/rename fails on names with capitals, spaces, or punctuation.

Common Root Causes

1. Emoji name wrapped in colons

reactions.add expects white_check_mark, not :white_check_mark:. The colons make it invalid.

2. Non-existent custom emoji

Reacting with a custom emoji name that isn’t installed in the workspace is invalid.

3. Skin-tone / alias mismatch

Aliases and skin-tone-modified names that Slack doesn’t recognise as-is are rejected.

4. Channel name violates rules

Channel names must be lowercase, no spaces/periods, and within length limits; violations return invalid_name (or name_taken if it merely collides).

How to diagnose

Reproduce the emoji case:

curl -s -X POST https://slack.com/api/reactions.add \
  -H "Authorization: Bearer $SLACK_BOT_TOKEN" \
  -H "Content-Type: application/json" \
  -d '{"channel":"C0123456789","timestamp":"1700000000.000100","name":":white_check_mark:"}'

{"ok": false, "error": "invalid_name"}

Verify a custom emoji exists before using it:

curl -s "https://slack.com/api/emoji.list" \
  -H "Authorization: Bearer $SLACK_BOT_TOKEN" | grep -o '"deploy_success"'

Fixes

• Strip the colons: pass white_check_mark, not :white_check_mark:.
• Validate custom emoji against emoji.list before reacting; fall back to a standard emoji if missing.
• Follow channel naming rules: lowercase, no spaces or periods, hyphens/underscores allowed, within the length limit.
• Normalise names in code (lowercase, trim, remove colons) before calling the API.

What to watch out for

• invalid_name (malformed/unknown name) differs from name_taken (a valid name that already exists) — the fixes are different.
• Emoji aliases can vary between workspaces for custom emoji; don’t assume a custom name exists everywhere.
• Building channel names from user input? Sanitise aggressively, or you’ll bounce between invalid_name and name_taken.

Related

• Slack Error: ‘name_taken’
• Slack Error: ‘message_not_found’
• Reaction-driven Slack automations for ops