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

1. Add JSON Dynamic Loader node to your workflow
2. Enter a json_path and sequence_number
3. Click Refresh Outputs
4. Outputs appear named after your JSON keys with correct types
5. 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:

1. Match by sequence_number field — scans batch_data for an entry whose sequence_number matches the input
2. Fallback to array index — if no match is found, uses sequence_number - 1 as the array index (clamped to bounds)
3. 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:

1. On execution, the node saves a temp preview (displayed in the node) and a permanent copy to input/{filename}.png
2. If a mask is connected, it is embedded as the PNG's alpha channel — LoadImage will automatically output it as its mask
3. 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