A collection of ComfyUI utility nodes: a dynamic JSON loader that auto-creates outputs from any JSON file, string/path helpers, and a preview-to-LoadImage bridge that lets you push generated images (with optional masks) into LoadImage nodes.

Features

Auto-discovery — reads JSON keys and exposes them as named outputs
Type detection — INT, FLOAT, STRING types with colored connectors
Batch support — sequence_number input for batch_data arrays
Connection-safe refresh — adding new keys preserves existing links
Workflow persistence — keys, types, and connections survive save/reload

Installation

ComfyUI Manager

Search for JSON Dynamic Loader in the ComfyUI Manager registry.

Manual

cd ComfyUI/custom_nodes/
git clone https://github.com/ethanfel/ComfyUI-JSON-Dynamic.git
# Restart ComfyUI

Usage

Add JSON Dynamic Loader node to your workflow
Enter a json_path and sequence_number
Click Refresh Outputs
Outputs appear named after your JSON keys with correct types
Connect to downstream nodes

Type Handling

| JSON type | Output type | Connector | |:---|:---|:---| | 42 (integer) | INT | Blue | | 3.14 (float) | FLOAT | Teal | | "hello" (string) | STRING | Pink | | true / false | STRING ("true" / "false") | Pink |

JSON Format

Flat JSON (single segment)

For simple use cases, the node reads keys directly from the root object. The sequence_number input is ignored.

{
  "general_prompt": "A cinematic scene...",
  "seed": 42,
  "flf": 0.5,
  "camera": "pan_left"
}

Batch JSON (multiple segments)

For multi-shot workflows, wrap entries in a batch_data array. Each entry is a segment representing one shot/scene with its own settings. The sequence_number input selects which segment to read.

{
  "batch_data": [
    {
      "sequence_number": 1,
      "general_prompt": "Wide establishing shot of a city",
      "seed": 42,
      "camera": "static",
      "flf": 0.0
    },
    {
      "sequence_number": 2,
      "general_prompt": "Close-up of the protagonist",
      "seed": 108,
      "camera": "pan_left",
      "flf": 0.5,
      "my_custom_key": "only on this segment"
    },
    {
      "sequence_number": 3,
      "general_prompt": "Aerial drone shot over rooftops",
      "seed": 77,
      "camera": "zoom_in",
      "flf": 0.8
    }
  ]
}

Segment lookup

The node resolves which segment to read using this logic:

Match by sequence_number field — scans batch_data for an entry whose sequence_number matches the input
Fallback to array index — if no match is found, uses sequence_number - 1 as the array index (clamped to bounds)
No batch_data — reads keys from the root object directly

This means segments don't need to be in order and can have gaps (e.g. 1, 5, 10). Each segment can have different keys — click Refresh Outputs after changing sequence_number if the keys differ between segments.

String & Path Utility Nodes

Four additional nodes that replace common multi-node chains for string and path operations.

Path Join (`utils/path`)

Joins 1–6 path segments using os.path.join with automatic normalization.

| Input | Type | Notes | |:---|:---|:---| | segment_1 | STRING | Required | | segment_2 – segment_6 | STRING | Optional |

Output: path (STRING)

String Format (`utils/string`)

Python format-string templating ({0}/{1:04d}.{2}) with up to 8 connected inputs. Handles zero-padding, type conversion, and arbitrary templates in one node.

| Input | Type | Notes | |:---|:---|:---| | template | STRING | Format string, e.g. {0}/{1:04d} | | v0 – v7 | any | Optional values to substitute |

Output: string (STRING)

String Extract (`utils/string`)

Extracts substrings with 3 modes:

| Mode | Description | |:---|:---| | split_take | Split on delimiter, take part at index (negative indices supported) | | between | Extract text between two delimiters | | filename_parts | Decompose path into dirname / basename / extension |

Outputs: result, dirname, basename, extension (all STRING)

String Switch (`utils/string`)

Boolean-based selection with built-in default values.

| Input | Type | Notes | |:---|:---|:---| | condition | BOOLEAN | Required | | on_true / on_false | any | Optional connected values | | default_true / default_false | STRING | Fallback widget values |

Output: result (any)

When a connected input (on_true/on_false) is present it takes priority; otherwise the corresponding default_* string widget is used.

Image Utility Nodes

Preview to Load Image (`utils/image`)

Previews an image like the built-in PreviewImage node, but also saves a copy to ComfyUI's input/ folder so you can push it into any LoadImage node with one click.

| Input | Type | Notes | |:---|:---|:---| | images | IMAGE | Required | | filename | STRING | Name for the saved file (without extension, default preview) | | mask | MASK | Optional — embedded as the PNG alpha channel |

Widgets (JS-side):

| Widget | Description | |:---|:---| | load_image_node_id | ID of the target LoadImage node | | Send to Load Image | Button — sets the target node's image selector to the saved file |

How it works:

On execution, the node saves a temp preview (displayed in the node) and a permanent copy to input/{filename}.png
If a mask is connected, it is embedded as the PNG's alpha channel — LoadImage will automatically output it as its mask
Enter the target LoadImage node's ID and click Send to Load Image — the target's image dropdown updates immediately, no restart needed

License

Apache 2.0